Sediments Contamination and Sustainable Remediation

Sediments Contamination and Sustainable Remediation Catherine Mulligan Masaharu Fukue Yoshio Sato Boca Raton London N...

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Sediments Contamination and

Sustainable Remediation Catherine Mulligan Masaharu Fukue Yoshio Sato

Boca Raton London New York

CRC Press is an imprint of the Taylor & Francis Group, an informa business

Co-published by IWA Publishing, Alliance House, 12 Caxton Street, London SW1H 0QS, UK Tel. +44 (0) 20 7654 5500, Fax +44 (0) 20 7654 5555 [email protected] www.iwapublishing.com 1-84339-300-X 978-1-84339-300-9

CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2010 by Taylor and Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Printed in the United States of America on acid-free paper 10 9 8 7 6 5 4 3 2 1 International Standard Book Number: 978-1-4200-6153-6 (Hardback) This book contains information obtained from authentic and highly regarded sources. Reasonable efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. The authors and publishers have attempted to trace the copyright holders of all material reproduced in this publication and apologize to copyright holders if permission to publish in this form has not been obtained. If any copyright material has not been acknowledged please write and let us know so we may rectify in any future reprint. Except as permitted under U.S. Copyright Law, no part of this book may be reprinted, reproduced, transmitted, or utilized in any form by any electronic, mechanical, or other means, now known or hereafter invented, including photocopying, microfilming, and recording, or in any information storage or retrieval system, without written permission from the publishers. For permission to photocopy or use material electronically from this work, please access www.copyright.com (http://www.copyright.com/) or contact the Copyright Clearance Center, Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01923, 978-750-8400. CCC is a not-for-profit organization that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Library of Congress Cataloging‑in‑Publication Data Mulligan, Catherine N. Sediments contamination and sustainable remediation / authors, Catherine N. Mulligan, Masaharu Fukue, and Yoshio Sato. p. cm. “A CRC title.” Includes bibliographical references and index. ISBN 978-1-4200-6153-6 (Taylor & Francis : alk. paper) -- ISBN 978-1-84339-300-9 (IWA : alk. paper) 1. Contaminated sediments--Management. 2. Soil remediation. 3. Sedimentation and deposition. I. Fukue, Masaharu. II. Sato, Yoshio, 1947- III. Title. TD878.M85 2010 628.1’68--dc22 Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com

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Contents Preface.......................................................................................................................ix The Authors............................................................................................................ xiii Chapter 1 Introduction to Sediment Contamination and Management.................1 1.1 1.2

Introduction................................................................................1 Sustainable Development and the Aquatic Geoenvironment.........................................................................3 1.3 Sources of Pollutants..................................................................3 1.4 Management of Contaminated Sediments.................................9 1.5 Natural Mitigation Processes................................................... 11 1.6 Bioaccumulation of Contaminants........................................... 12 1.7 Sustainable Sediment Management Practices.......................... 14 1.8 Concluding Remarks................................................................ 16 References........................................................................................... 17 Chapter 2 Introduction to Sediments................................................................... 19 2.1 2.2 2.3

Introduction.............................................................................. 19 Definition of Sediments............................................................ 21 Types of Sediments.................................................................. 21 2.3.1 Types of Sediments by Components........................... 22 2.3.1.1 Primary Minerals........................................ 23 2.3.1.2 Secondary Minerals..................................... 23 2.3.1.3 Organic Matter.............................................24 2.3.1.4 Oxides and Hydrous Oxides........................24 2.3.1.5 Carbonates and Sulfates..............................24 2.3.2 Types of Sediments by Grain Size..............................24 2.3.3 Structure of Sediments................................................26 2.4 Benthos..................................................................................... 30 2.5 Uses of Sediments and Water................................................... 31 2.6 Management of Sediments....................................................... 32 2.7 Concluding Remarks................................................................ 33 References........................................................................................... 33 Chapter 3 Contaminant–Sediment Interactions................................................... 35 3.1 3.2

Introduction.............................................................................. 35 Factors Influencing Contaminant–Sediment Interactions........ 35 3.2.1 Specific Surface Area (SSA)....................................... 35 3.2.2 Cation Exchange Capacity (CEC)............................... 39 iii

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3.3

Sorption of Pollutants and Partition Coefficients..................... 41 3.3.1 Partitioning of Inorganic Pollutants............................44 3.3.2 Selective Sequential Extraction................................... 47 3.3.3 Organic Chemical Pollutants...................................... 50 3.4 Biotransformation and Degradation of Organic Chemicals and Heavy Metals................................................... 54 3.4.1 Bioremediation Processes........................................... 56 3.4.2 Bioattenuation and Bioavailability.............................. 58 3.5 Interaction of Contaminants, Organisms, and Sediments........ 59 3.5.1 Bioaccumulation.......................................................... 59 3.5.2 Bioturbation.................................................................60 3.6 Chemical Reactions, Geochemical Speciation, and Transport Predictions............................................................... 62 3.7 Concluding Remarks................................................................64 References........................................................................................... 65 Chapter 4 Remediation Assessment, Sampling, and Monitoring........................ 71 4.1 4.2 4.3 4.4

4.5 4.6 4.7

Introduction.............................................................................. 71 Cleanup Goals and Background Values................................... 72 Sampling................................................................................... 72 Analysis and Evaluation........................................................... 77 4.4.1 Mechanical Properties................................................. 77 4.4.1.1 Strength for Sediments................................ 77 4.4.1.2 Consolidation............................................... 79 4.4.2 Physical Properties...................................................... 79 4.4.2.1 Sediment Temperature................................. 79 4.4.2.2 Grain Size....................................................80 4.4.2.3 Specific Gravity........................................... 81 4.4.3 Chemical Sediment Quality........................................ 82 4.4.3.1 pH................................................................ 82 4.4.3.2 Organic Pollution Indicators........................ 83 4.4.3.3 Total Organic Carbon (TOC)...................... 83 4.4.3.4 Loss on Ignition (Ignition Loss).................. 83 4.4.3.5 Nitrogen.......................................................84 4.4.3.6 Phosphorus................................................... 85 4.4.3.7 Toxic Substances—Trace Metals................. 86 4.4.3.8 Toxic Substances—Organic Micropollutants............................................ 88 4.4.3.9 Other Environmental Indicators..................90 4.4.3.10 Test Kits....................................................... 91 Decision Making Using Indicators...........................................92 Case Studies............................................................................. 93 4.6.1 Investigation of Port Sediments.................................. 93 4.6.2 Lake Sediments...........................................................97 Concluding Remarks.............................................................. 102

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References......................................................................................... 105 Chapter 5 Natural Recovery of Contaminated Sediments................................. 109 5.1 5.2 5.3 5.4

Introduction............................................................................ 109 Natural Recovery Processes of Sediments............................. 111 Evaluation of the Natural Recovery of Sediments................. 113 Models for Natural Remediation............................................ 119 5.4.1 Deposition Rate......................................................... 121 5.4.2 Source Loading......................................................... 121 5.4.3 Hydrodynamic Parameters........................................ 121 5.5 Regulatory Framework........................................................... 122 5.6 Protocols Developed for Monitored Natural Recovery.......... 122 5.7 Case Studies of Natural Recovery.......................................... 124 5.8 Enhanced Natural Recovery................................................... 129 5.9 Concluding Remarks.............................................................. 130 References......................................................................................... 131

Chapter 6 In Situ Remediation and Management of Contaminated Sediments.......................................................................................... 135 6.1 6.2

Introduction............................................................................ 135 In Situ Capping....................................................................... 135 6.2.1 Design Factors for Sand Capping.............................. 137 6.2.1.1 Consolidation............................................. 137 6.2.2 Rough Estimate of Cap Thickness for Advection..... 140 6.2.2.1 Contaminant Transport.............................. 142 6.2.3 Active Capping.......................................................... 144 6.3 Rehabilitation of the Coastal Marine Environment............... 144 6.3.1 Eutrophication........................................................... 145 6.3.2 Contamination........................................................... 145 6.3.3 Distribution of Contaminated Particles..................... 146 6.3.4 Resuspension Method for Removal of Contaminated Sediment Particles............................. 147 6.3.5 Technology for Sediment Remediation by Resuspension............................................................. 148 6.3.6 Design of a Filter Unit............................................... 149 6.4 Chemical Remediation Technologies..................................... 150 6.5 Biological Remediation Technologies.................................... 153 6.6 Creation of Seaweed Swards.................................................. 156 6.7 Case Studies of Remediation.................................................. 158 6.7.1 Contaminated Sediment Capping Projects............... 158 6.7.2 Steel Slag................................................................... 159 6.7.3 Bioremediation.......................................................... 161 6.8 Concluding Remarks.............................................................. 163 References......................................................................................... 164

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Chapter 7 Dredging and the Remediation of Dredged Contaminated Sediments.......................................................................................... 169 7.1 7.2 7.3

Introduction............................................................................ 169 Sustainable Dredging Strategies............................................. 171 Physical Remediation Technologies....................................... 172 7.3.1 Physical Separation................................................... 173 7.3.2 Sediment Washing..................................................... 174 7.3.3 Flotation.................................................................... 180 7.3.4 Ultrasonic Cleaning.................................................. 180 7.4 Chemical/Thermal Remediation............................................ 180 7.4.1 Oxidation................................................................... 182 7.4.2 Electrokinetic Remediation....................................... 183 7.4.3 Solidification/Stabilization........................................ 185 7.4.4 Vitrification............................................................... 186 7.4.5 Thermal Extraction................................................... 189 7.5 Biological Remediation.......................................................... 190 7.5.1 Slurry Reactors.......................................................... 191 7.5.2 Landfarming.............................................................. 191 7.5.3 Composting............................................................... 193 7.5.4 Bioleaching................................................................ 195 7.5.5 Bioconversion Processes........................................... 195 7.5.6 Phytoremediation...................................................... 195 7.6 Beneficial Use of Sediments................................................... 196 7.7 Confined Disposal.................................................................. 198 7.8 Comparison between Treatment Technologies.......................200 7.9 Case Studies of Remediation.................................................. 201 7.9.1 Remediation of Sediments Contaminated with Dioxin........................................................................ 201 7.9.2 Dredging Case Study................................................202 7.9.3 Case Study of a Washing Process.............................204 7.9.4 Biotreatment Case Study...........................................204 7.10 Concluding Remarks..............................................................206 References.........................................................................................209

Chapter 8 Management and Evaluation of Treatment Alternatives for Sediments.......................................................................................... 215 8.1 8.2 8.3 8.4 8.5

Introduction............................................................................ 215 Generic Framework................................................................ 215 Remediation Objectives.......................................................... 216 Lines of Evidence................................................................... 219 Evaluation of the Management Alternatives.......................... 219 8.5.1 MNR.......................................................................... 221 8.5.2 Dredging.................................................................... 222 8.5.3 In Situ Capping.......................................................... 223

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8.6 Selection of Technologies.......................................................224 8.7 Management Plan................................................................... 226 8.8 Sustainable Remediation........................................................ 234 8.9 Strategy for Remediated Sediment Sustainability................. 235 8.10 Concluding Remarks.............................................................. 238 References......................................................................................... 239 Chapter 9 Current State and Future Directions................................................. 241 9.1 Introduction............................................................................ 241 9.2 Disposal at Sea....................................................................... 242 9.3 Beneficial Use of Dredged Materials..................................... 243 9.4 Sustainability Evaluation........................................................246 9.5 Case Study of Lachine Canal................................................. 249 9.6 Barriers to Technology Development and Implementation.... 253 9.7 Current Needs and Future Directions.................................... 253 9.8 Concluding Remarks.............................................................. 257 References......................................................................................... 258 Appendix A Sediment Quality Guidelines from Environment Canada and MDDEP, 2008................................................................................... 261 References.........................................................................................266 Appendix B London Convention and Protocol: Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, 1972................................................................................................... 267 Introduction....................................................................................... 267 The 1978 Amendments—Incineration.............................................. 268 The 1978 Amendments—Disputes......................................... 268 The 1980 Amendments—List of Substances.................................... 268 The 1989 Amendments...................................................................... 268 The 1993 Amendments...................................................................... 269 1996 Protocol.................................................................................... 269 Permitted Dumping................................................................ 270 2006 Amendments to the 1996 Protocol........................................... 271 Appendix C Prediction of Sediment Toxicity Using Consensus Based Freshwater Sediment Quality Guidelines: USGS. 2000. Prediction of sediment toxicity using consensus based freshwater sediment quality guidelines. EPA 905/R-00/007, June 2000.......................................................................................... 273 References......................................................................................... 275 Appendix D International Sediment Quality Criteria........................................... 277 Hong Kong........................................................................................ 278 The Republic of Korea...................................................................... 279 Australia and New Zealand............................................................... 279

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Australia and New Zealand Guidelines for Fresh and Marine Water Quality................................................ 279 National Ocean Disposal Guidelines for Dredged Material...................................................... 279 Canada............................................................................................... 279 United States..................................................................................... 279 USEPA ................................................................................... 279 USACE ...................................................................................280 U.S. State Guidelines..............................................................280 Florida ...................................................................280 New York................................................................... 281 Washington State....................................................... 281 Sediment Quality Chemical Criteria................................................. 281 Wisconsin..........................................................................................284 Europe...............................................................................................284 European Legislation..............................................................284 EC Legislation...........................................................284 Classification of Dredged Material in the EC Region........................................................284 Belgium..................................................................................284 Finland ................................................................................... 285 France ....................................................................................286 Germany................................................................................. 286 Ireland .....................................................................................288 The Netherlands...................................................................... 288 Norway ................................................................................... 292 Portugal................................................................................... 293 Spain ...................................................................................... 293 Sweden ................................................................................... 294 The United Kingdom.............................................................. 294 Qatar.........................................................................................296 Index.......................................................................................................................297

Preface The surface water environment is an important part of the geoenvironment. It is the recipient of (a) liquid discharges from surface runoffs, rivers, and groundwater and (b) waste discharges from land-based industrial, municipal, and other anthropogenic sources. It is also a vital element that provides the base for life support systems and is a significant resource. The combination of these two large factors, with their direct link to human population, makes it an integral part of the considerations on the sustainability of the geoenvironment and its natural resources. A healthy ecosystem ensures that aquatic plants and animals are healthy and that these do not pose risks to human health when they form part of the food chain. In this book, we will discuss (a) the threats to the health of the sediments resulting from discharge of pollutants, excessive nutrients, and other hazardous substances from anthropogenic activities, (b) the impacts observed as a result of these discharges including the presence of hazardous materials and the phenomenon of eutrophication, (c) the remediation techniques developed to restore the health of the sediments, and (d) how to evaluate the remediation technologies using indicators. Therefore, the problem of sediment contamination is developed, in addition to how the sediments can be remediated and how the treatments can be evaluated. Contaminated sediments are a risk to fish, humans, and animals that eat the fish. Although part of the geoenvironment, sediments have received much less attention from researchers, policy makers, and other professionals than other components. Sediment, however, is an essential and valuable resource in river basins and other aqueous environments. A large biodiversity exists in the sediments. It is thus a source of life and resources for humans as construction materials, sand for beaches, and farmland and wetland nutrients. There is a need to develop a better understanding of the sediment–water environment and better management practices due to their potential impact on human health and the environment. In particular, they need to be considered during efforts to meet sustainability requirements. Sediments can be exposed to multiple sources of contaminants and are located at the bottom of water columns. This makes risk assessment and management more difficult than in soils. The benthic community cannot be isolated from the contaminated sediments. This community is at the base of the aquatic food chain, but can be highly tolerant to the contaminants. Sediment quality criteria thus are much lower than for soils because the sediments can have a significant influence on the aquatic food chain. Sediments have been removed for centuries by dredging for maintaining navigation. This type of sediment management will not be elaborated on substantially because sediment management for the purpose of environmental cleanup or management will be the main focus of this book. The binding of the contaminants to the sediments, their bioavailability, mobility, and degradability are all important aspects ix

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that will be taken into account. More than 10% of the sediments have been estimated to be contaminated in the United States. In Chapter 1, we will focus on the introduction of the importance of sediments, the sources of contaminants, management practices, and sustainability. Sediments are found in lakes, rivers, streams, harbors, and estuaries after traveling downstream from their origin. Sources of effluents containing the solids include urban, agricultural, and industrial lands. Strategies for remediation of contaminated sediments are introduced. In Chapter 2, sediment components are discussed. They are inorganic and organic solid materials and are often classified by size, as gravel, sand, silt, and clay. The term “sediments” is used for soils deposited in water. They are often called marine soils, if it is settled in the marine environment. Thus, sediments are in contact with inorganic, organic, and other human-discharged materials, through the influence of the pore water. Therefore, the properties of the pore water are an important factor regarding the quality of the sediments. Sediment uses are also described. The interactions of the pore water with the contaminants and the solids are complex and will be discussed in Chapter 3. It is important to understand the physical and physicochemical interactions of the contaminants with the sediment solids to understand the capacity of retention of the sediments and potential parameters for contaminant release. Sediment composition, properties, and characteristics will influence the interactions at the sediment–pore water interface. The reactions between pollutants and sediment will determine its transport through the sediments, and also its fate. Sediment quality is related to the quality of surface water. It is due to the serial mechanisms of the dissolution of organic matter and the exclusion of contaminants due to the consolidation of sediments or the leaching of contaminants. Therefore, in order to make an appropriate assessment of sediments, the physical, chemical, and biological mechanisms have to be understood well. Since the mechanisms are natural and complex, there is the possibility that nonpredictable results can be obtained. Therefore, it is necessary for engineers to modify or take measures suited to the occasion. In Chapter 4, information including sampling and physical, chemical, and biological test procedures to determine the state and extent of contamination will be examined. Sampling can also be used to predict future trends or to evaluate the progress of the remediation work. The scale for sampling and monitoring will be site dependent. Since most of the physical and chemical properties of sediments have to be determined by the laboratory tests, sampling is almost always needed. Therefore, monitoring of sediment properties can be achieved by tests on samples obtained from the sites. Thus, much effort and planning is required for the monitoring of sediments. In Chapter 5, the mechanisms involved and case studies of natural recovery of various pollutants at contaminated sediment sites will be examined. There are differences in the type of processes that play a role in the natural attenuation of groundwater and the natural recovery of sediments. Usually transformation processes of the contaminants are more dominant in the natural attenuation of surface soils, whereas isolation and mixing are more prevalent in sediments. Natural recovery includes both attenuation aspects (reduction of contaminants with no transport to other media) and recovery (which allows the benthic and pelagic communities to be reestablished and resume their beneficial uses). Monitoring is required to ensure that the remediation

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objectives are achieved and that it is proceeding as planned. Thus the term monitored natural recovery (MNR) is used. Thus upon successful completion, MNR would meet the needs of sustainability. Acceptance is increasing as there is substantial cost reduction achieved due to the nonremoval of large volumes of sediments. There are still many gaps in knowledge, and a careful evaluation of the management options must be made. Techniques for the remediation of sediments may be required when the sediment leads to the accumulation of contaminants in aquatic life or when the release of hazardous materials from sediments becomes a serious problem. Therefore, a remediation technique, such as capping, dredging, or physical, biological, and/or chemical treatment, has to be considered. In Chapter 6, in situ remediation techniques and the management of contaminated sediments will be described. In situ remediation could be beneficial over dredging due to a reduction in costs and lack of solid disposal requirements. Therefore, these methods will be examined. In Chapter 7, dredging and the management of dredged sediments will be discussed. Dredging is the excavation of materials (sediments) from the bottom of the water column for a number of different purposes and is often required for navigational purposes in coastal and inland waters and/or removal of contaminated sediment. The dredging process itself has the potential to impact the environment. Proper design of the dredging project can minimize the environmental impact. Long-term monitoring is rarely performed to determine the residual contamination and longterm effects of the dredging. The use of different methodologies includes physicochemical to biological approaches to the management of different routes of disposal or uses of the dredged material. Selection of the most appropriate remediation technology must coincide with the environmental characteristics of the site and the ongoing fate and transport processes and is elaborated on in Chapter 8. To be sustainable, the risk at the site must be reduced, and the risk should not be transferred to another site. The treatment must reduce the risk to human health and the environment. Cost-effectiveness and permanent solutions are significant factors in determining the treatment. Sites vary substantially, and there can be substantial uncertainty involved in the evaluation process. However, decisions must be made based on the information available. In this chapter, we will examine the means to select the most appropriate technique for site remediation, evaluate the progress of the remediation, and determine the long-term restoration of the site. Finally, in Chapter 9, the two main approaches, in situ and ex situ treatment, are examined further. Environmental dredging requires evaluation of the risks of dredging, determination of disposal methods, and/or potential beneficial use. Depending on site conditions, in situ management may be preferable and may pose less risk to human health, fisheries, and the environment. Both short-term and long-term risks must be evaluated for the in situ and ex situ options. To work toward sustainability, waste must be minimized, natural resources must be conserved, landfill deposition should be minimized, and benthic habitats and wetlands must not be lost and must be protected. Innovative integrated decontamination technologies must be utilized. We will examine, also, where developments are needed. The fate and transport of contaminants must be understood more thoroughly to develop appropriate strategies. Sediment quality standards and guidelines and conventions are detailed in the appendices.

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We wish to acknowledge the benefit of all the interactions and discussions we have had with all colleagues, research students, and professionals in the field. They are all a vital part of the education of the public, industry, and governmental bodies that are involved in the conservation and protection of the natural resources. A longterm vision is needed. Otherwise, natural resources will continue to be depleted, landfills will continue to be filled with contaminated sediments, and biodiversity in the aquatic geoenvironment will be diminished. Integrated innovative management practices need to be developed and applied. Catherine N. Mulligan Masaharu Fukue Yoshio Sato

The Authors Catherine N. Mulligan has B.Eng. and M.Eng. degrees in chemical engineering and a Ph.D. specializing in geoenvironmental engineering from McGill University, Montreal, Canada. She has gained more than 20 years of research experience in government, industrial, and academic environments. She was a research associate for the Biotechnology Research Institute of the National Research Council and then worked as a research engineer for SNC Research Corp., a subsidiary of SNC‑Lavalin, Montreal, Canada. She then joined Concordia University, Montreal, Canada, in the Department of Building, Civil and Environmental Engineering. She has taught courses in site remediation, environmental engineering, fate and transport of contaminants, and geoenvironmental engineering, and she conducts research in remediation of contaminated soils, sediments, and water. She holds a Concordia Research Chair in Geoenvironmental Sustainability. She has completed a textbook (Environmental Biotreatment, Government Institutes, 2002) as a sole author on biological treatment technologies for air, water, waste, and soil, and two others, with Professor R.N. Yong (Natural Attenuation of Contaminants in Soil, CRC Press, 2004) and with Professors R.N. Yong and M. Fukue (Geoenvironmental Sustainability, CRC Press, 2006). She has authored more than 50 refereed papers in various journals and holds three patents. She is a member of the Order of Engineers of Quebec, Canadian Society of Chemical Engineering, American Institute of Chemical Engineering, Air and Waste Management Association, Association for the Environmental Health of Soils, American Chemistry Society, Canadian Society for Civil Engineering, and the Canadian Geotechnical Society. Masaharu Fukue has B.Eng. and M.Eng. degrees in civil engineering from Tokai University, Japan, and a Ph.D. in geotechnical engineering from McGill University, Montreal, Canada. He joined a consultant firm for a short period and then moved to Tokai University. He has given courses in geoenvironmental engineering, hydrospheric environment, shipboard oceanographic laboratory, and submarine geotechnology. He is a member of the International Society for Soil Mechanics and Geotechnical Engineering, International Society for Terrain-Vehicle Systems, Japanese Society for Civil Engineers, the Japanese Geotechnical Society, and the Japan Society of Waste Management Experts. He served as a chief editor for Japanese Standards for Soil Testing Methods and for Japanese Standards for Geotechnical and Geoenvironmental Investigation Methods. He also served as a director of the Standard Division and a member of the Board of Directors of the Japanese Geotechnical Society. Since 1996 he has been a member of the editorial board of the American journal Marine Georesources and Geotechnology. He was recently a chair of the organizing committee of the 3rd International Symposium on Contaminated Sediments, sponsored by ASTM, ISCS2006-Shizuoka, Japan. He is also an advocate and a promoter of the Annual Symposium on Sea and Living Things and Rehabilitation of Coastal Environment, Japan. He has sponsored the Marine xiii

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Geoenvironmental Research Association in Japan. He invented a filtration system for seawater using a 2500-ton large barge and performed a field experiment using the system for seawater purification in a small bay. He has published more than 300 scientific papers on qualities of seawater, sediments, and soils, has completed a book with Professors R.N. Yong and C.N. Mulligan, Geoenvironmental Sustainability (CRC Press, 2006), and is co-editor of Contaminated Sediments: Evaluation and Remediation Techniques, STP 1482, ASTM International, 2006. Yoshio Sato has B.Sci. and Dr.Sci. degrees in oceanography from Tokai University, Japan. He has had more than 30 years of research and teaching experience in the university. His specialty is chemical analyses of the formation mechanism of manganese nodules on the ocean floor. Recently, he has become interested in preservation of the environment of enclosed sea areas, the utilization of ground seawater for fishery, and deep ocean seawater. He is a member of the Chemical Society of Japan, the Oceanographic Society of Japan, the Geochemical Society of Japan, the Society of Sea Water Science, Japan, and the Japan Association of Deep Ocean Water Applications. He is a member of a committee for prevention of pollution in Shizuoka Prefecture, Committee of Environment in Shizuoka Prefecture, and Committee of Environment in Shizuoka City. He is a member of the board of directors of the Society of Sea Water Science, Japan, and has published more than 100 papers about seawater.

to 1 Introduction Sediment Contamination and Management 1.1 Introduction Approximately 0.9 billion m3 of sediment in the United States are contaminated, which are a risk to fish, humans, and animals that eat the fish, according to the United States Environmental Protection Agency (USEPA, 1998). The rate of survival, immunity to diseases, and growth of fish such as salmon may be affected by exposure to contaminated sediments early in life (Varanasi et al., 1993). Although part of the geoenvironment, sediments have received much less attention from researchers, policy makers, and other professionals than other components. Sediment, however, is an essential and valuable resource in river basins and other aqueous environments. A large biodiversity exists in the sediments. It is thus a source of life and resources for humans as construction materials, sand for beaches, and farmland and wetland nutrients. However, due to the close contact of sediments with the water environment, they are both a source and a sink for contaminants. There is a need to develop a better understanding of the sediment–water environment and better management practices due to their potential impact on human health and the environment. In particular, they need to be considered during efforts to meet sustainability requirements. Some of the major impacts due to increasing population pressures include: • • • • •

Loss of biodiversity and living resources Increased production of wastes and pollutants Depletion of nonrenewable natural resources Decreased soil, water, and air quality Increased discharges of greenhouse gases

Although some of these issues have been examined previously in regard to the geoenvironment (Yong et al., 2006), in this book, we will focus on the stresses and how to mitigate the impacts of these factors in relation to sediments, because they are a highly important resource and basis for life. This environment will be defined as the aquatic geoenvironment (Figure 1.1). They form an integral part of a functioning ecosystem and partake in various types of physical, chemical, and biological activities. Some of these as detailed by Trevors (2003) include partaking in various cycles such as those of carbon, nitrogen, phosphorus, and sulfur, in addition to the 1

2

Sediments Contamination and Sustainable Remediation Ecosphere

Geosphere

Atmosphere Hydrosphere

Also called Lithosphere includes solid continental mantle, continental and oceanic crust, and extending downward

Terra firma

Biosphere

Includes all the water bodies on the earth’s surface

All receiving waters on terra firma ma s, (lakes, rivers, ponds, wetlands, estuaries, groundwater, aquifers) rs)

Life zone including all living organisms within and above the sediments

Aquatic life zones

Aquatic Geoenvironment

Figure 1.1 The various constituents of the ecosphere and their relationship to the aquatic geoenvironment.

hydrologic and natural processes for the control of the biodegradation of pollutants in the sediment and water. Sediment is defined by SedNet as “suspended or deposited solids, acting as a main component of a matrix which has been or is susceptible to being transported by water” (Brils, 2003). Soil is defined as an aggregate material covering the earth surface which consists of solid particles and void spaces with liquid and gas. Soil particles are composed of inorganic and organic solid materials and are often classified by size, as gravel, sand, silt, and clay (which will be discussed in more detail in Chapter 2). The term “sediments” is used for soils deposited in water. They are often called marine soils, if they are settled in the marine environment. Sedimentary rock is, therefore, consolidated and cemented sediment. Sediments can be exposed to multiple sources of contaminants and are located at the bottom of water columns. This makes risk assessment and management more difficult than for soils. The benthic community cannot be isolated from the contaminated sediments (USEPA, 2002). This community is at the base of the aquatic food chain, but can be highly tolerant to the contaminants (USEPA, 1998). Sediment quality criteria thus are much lower than for soils because the sediments can have a significant influence on the aquatic food chain. More than 10% of the volume of sediments (the upper 5 cm) at the bottom of the U.S. surface waters have been estimated to be contaminated.

Introduction to Sediment Contamination and Management

3

1.2 Sustainable Development and the Aquatic Geoenvironment Five major themes under the acronym sustainable development were identified in the Johannesburg World Summit on Sustainable Development (WSSD 2002). They included (1) water and sanitation, (2) energy, (3) health, (4) agriculture, and (5) biodiversity. It can easily be seen how many of these activities can influence sediment quality. The impact of development activities with four components can be substantial. The components include industrialization, urbanization, resource exploitation, and agriculture (food production) (Figure 1.2). Sediments are found in lakes, rivers, streams, harbors, and estuaries after traveling downstream from their origin. Sources of effluents containing the solids include urban, agricultural, and industrial lands. Sediments have been removed for centuries by dredging for maintaining navigation. This type of sediment management will not be elaborated on substantially, because sediment management for the purpose of environmental cleanup or management will be the main focus of this book along with the assessment of the sediments. The binding of the contaminants to the sediments, their bioavailability, mobility, and degradability are all important aspects that will be examined.

1.3 Sources of Pollutants Point and diffuse pollution sources enter the aquatic environment. Agricultural, urban, and industrial activities, spills, and accidents contribute to the pollution. Manufacturing and energy production, urban centers, municipalities, service industries, airborne and groundwater-transported contaminants all contribute contaminants to the sediments. In general, these effluents are either surface runoffs that Energy

Water and soil

Natural resources

Productivity Industrialization

Agriculture and food production

Urbanization

Goods and services – food, shelter, clothing Sustainable society

Sustainable development Figure 1.2 Basic elements and interactions contributing to a sustainable society and to sustainable development.

4

Sediments Contamination and Sustainable Remediation

discharge into the rivers, lakes, and groundwater or are point sources (Figure 1.3) from municipal, industrial, or other sources. Dredging is commonly used for maintenance of navigational routes. The material has been reused for building and construction materials. Extraction of oil and other resources is also frequent below the water surface, such as oil from Hibernia platforms of the coast of Newfoundland, Canada.

1. The use of the marine environment for fish and seafood extraction is one of the oldest industries. More recently, fish aquaculture is growing in popularity as fish stock become more and more depleted. 2. Water is extracted commonly for drinking water and for hydroelectric power generation. 3. Although waste disposal is most frequently on land, a lack of suitable land surfaces is now forcing waste disposal facilities in countries like Japan to be placed in marine landfills in special facilities.

Some of these contaminant sources and how they reach the marine geoenvironment can be seen in Figure 1.4. Proper management means that the impact must eliminate or minimize damage to the ecosystem and the entry of these pollutants into the environment. Spills, leaks, discharge, and runoff all threaten water quality and subsequently health, two of the main components of WEHAB.

Industrialization, Urbanization, Resource Exploitation Waste streams, waste containment systems, Emissions; Discharges; Tailings ponds; Dams, Landfills; Barrier systems; Liners; Offshore oil drilling

Agricultural Activities Farm wastes, Soil erosion, Compaction, Organic matter loss, Nitrification, Fertilizers, Insecticides; Pesticides, Non-point source pollution

Sediment and Water Quality, and Threat Management Point and non-point source pollution; Aquifer, Groundwater, Surface Water, Watershed, Receiving Waters e.g. lakes, ponds, rivers, streams, etc.

Site Contamination, Management, and Remediation

Sediment contamination; Pollution management and control; Toxicity reduction; Concentration reduction; Remediation and technology; Land suitability; Restoration and rehabilitation; Threat reduction and curtailment

Figure 1.3 Threats and waste streams impacting soil and water quality.

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Spills, diffuse discharges from harbour activities and boats, etc.

Precipitation falling through atmosphere with noxious gases and airborne pollutants

Runoff of ground surfaces polluted with nutrients, herbicides, pesticides, etc.

Pollutant plume from leaching of waste piles and industrial discharges, AMD

Runoff Groundwater flow

River

Unconfined aquifer

Aquitard

Urban and domestic discharges, etc.

Confined aquifer

Figure 1.4 Some of the more prominent causes of pollution of recharge water for rivers, other receiving waters, and groundwater (aquifers). Contamination of the confined aquifer depends on whether communication is established with the unconfined aquifer.

Heavy metals are common inorganic pollutants in the geoenvironment. These include: • From atomic numbers from 22 to 34: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, and Se • From 40 to 52: Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, and Te • From 72 to 83: Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, and Bi Anthropogenic activities such as landfills, metal extraction, and metal plating generate heavy metal leachates containing copper, lead, zinc, and so on. A more detailed description of the various forms and sources of arsenic, cadmium, chromium, copper, lead, nickel, and zinc can be found in Yong et al. (2006). Recently, extensive investigations were performed in the Port Jackson estuary in southeastern Australia, near Sydney, due to the 2000 Olympic Games (Birch and Taylor, 1999). Eight metals were measured in more than 1700 surface sediment samples in the 30-km estuary, river tributaries, harbor annexes, and canals. Copper, lead, and zinc, in particular, were found upstream where there were extensive industrial and commercial activities. Thunderstorms and flooding transported the metals downstream. Total levels of copper, lead, and zinc in the estuarine sediment corresponded to 1,900, 3,500, and 7,300 tonnes, respectively, due to many decades of

6


industrial discharges. Aquatic flora and fauna were affected by the sediments. In the late 1990s, a program for reduction of waste discharges was initiated. However, remediation of the sediments will be complex. Organic chemical pollutants originate from chemical-producing industries such as refineries, the spillage and leakage of various chemicals such as petroleum products, the use of various products such as paints, greases, oils, pesticides, etc. A common way to group the contaminants is as hydrocarbons, which can be divided into monocyclic, polycyclic hydrocarbons, alkanes, alkenes, etc., or as organohalides, which contain halides such as chlorine. Polycyclic chlorinated biphenyls (PCBs) and trichloroethylene (TCE) are examples of the latter. Organic compounds may also contain oxygen or nitrogen atoms such as methanol or trinitrotoluene (TNT). The aquatic environment is a resource that must be protected and maintained in a healthy state. When the health of plants and animals that are part of the food chain is impacted, then there is a risk as well to human health. Water is of primary importance for all forms of life. Surface water and groundwater are the primary sources of drinking water. Human activity has numerous influences on the hydrologic cycle. The main processes in the cycle include evaporation and transpiration, condensation, precipitation, infiltration, and runoff. Humans have significantly altered natural runoff and infiltration patterns and the balance between these two processes. Construction of impermeable surfaces such as roads, highways, and parking lots in urban areas create impermeable surfaces that increase runoff and decrease infiltration. The runoffs subsequently are sent to storm drains or other drainage systems, reducing aquifer levels. Soil compaction during agricultural processes will also increase runoff rates. The transport of contaminants including pesticides, herbicides, insecticides, animal wastes, etc. is increased via runoff, which often reaches surface waters (ponds, lakes, rivers, etc.). Managed runoffs are channeled via sewers and drains and can be discharged with or without treatment. The waters often contain suspended solids that will ultimately become sediments. The dissolved pollutants also may concentrate on the already present sediments. Untreated discharge can reduce water quality substantially. Pollutant source elimination or mitigation of the pollution needs to be practiced, in addition to water treatment. Water is a highly precious resource. Less than 5% is nonsaline (Yong, 2001), while only 0.2% and 0.3% is found in lakes and rivers, respectively. In addition, more than half to the world’s animal and plant species live in the water. Thus protection of water quality is highly important. Decreased water quality decreases the water quantity available, particularly where the need is urgent. In developing countries water use is increasing. Rapid industrialization and urbanization leads to poor water of insufficient quantities. Water management practices need substantial improvement to protect ecosystems and public health. Monitoring of river, lake water, and sediment is not frequently conducted, and therefore the locations of pollutant sources, intensity, and impact are difficult to determine. Only a limited number of parameters such as microbial counts are determined. Agriculture uses large quantities of water. Water use per crop grown needs to be optimized. Pollutant sources include insecticides, pesticides, fungicides, and fertilizers. Herbicides and pesticides are persistent and can accumulate in animal


7

tissues. Nutrients such as nitrates from runoff of animal wastes from pigs or poultry can severely impact water quality of lakes and rivers (Yamaska River in Quebec, Canada, for example). Detergents are other sources of nutrients. Accumulation of the nutrients can lead to eutrophication and subsequent decreases in water color, taste, and odor. Intensive farming practices have led to increases of phosphorus levels in the lakes. A lack of nutrient treatment processes for wastewater has also contributed. Lake water eutrophication is thus becoming an extensive problem. Elevated nutrients are currently found in many surface waters, and thus even if the input of nutrients is totally eliminated, recovery may take up to 10 years due to slow flushing rates (WHO, 1999). Elevated levels of nitrogen and phosphorus increase the activity of phytoplankton, macrophytes, and other algal groups. Cyanobacteria, which can fix nitrogen, then may replace phytoplankton, altering the benthic community and other species in the ecosystem. Oxygen becomes depleted, destroying flora and fauna, in the water and at the bottom of the water column. Carbon accumulation occurs, followed by asphyxia and mortality of biota. Nitrogen ingestion by humans can lead to blue-baby syndrome in infants in particular. Sanitary risks can also increase due to ingestion of nitrate-containing water. Worldwide consumption of fertilizers has increased from 14 to 140 million tons from 1940 to 1999 (Chamely, 2003). One-tenth of these fertilizers contain phosphorus, and one-half contain nitrogen. Farming waste, excrement, inadequately maintained septic tanks, and detergents are other contributing factors. Nitrates are easily leached from the soil because both nitrates and the clay particles in the soil are negatively charged. Poor agricultural practices and drainage of the fertilizers increases the nitrate contents in many of the European rivers such as the Meuse (4 mg/L), Rhine (3 mg/L), Loire and Po (2 mg/L), and Rhone (1.5 mg/L) (Chamely, 2003). North American rivers such as the Mississippi (1 mg/L) and the Saint Lawrence Rivers (0.25 mg/L) tend to be lower. These levels have been increasing since the 1960s. The other site is the des Hurons River, which is a tributary of the Richelieu River that joins the river on the eastern bank of the Chambly Lake, located east of Montréal, Quebec, and extends 35 to 40 km northeast of the Chambly Lake. The area of the des Hurons River is an intensive farming one with corn and wild plants. The river receives high loads of soil and nutrients due to the agricultural activities in the area. The average of suspended solids (SS) concentration in the des Hurons River in 2007 and 2008 varied from 5.6 mg/L to 134.0 mg/L, and that of chemical oxygen demand (COD) and total phosphorus (T-P) varied from 9.0 mg/L to 26.2 mg/L and 0.05 mg/L to 0.43 mg/L, respectively (Inoue et al., 2009). In Europe, phosphate discharges have been controlled since the ban on phosphate-containing detergents in 1985. Levels increased from 10 to 90 µg/L in Lake Geneva from the 1960s to the 1970s but have decreased to 50 µg/L in the 1990s (Chamley, 2003). The mining industry discharges their wastes into storage dumps, holding ponds, tailings ponds, and other systems. They can leak, or the structures can fail, allowing discharges into surface water, thus impacting the sediments. Heavy metals in particular are the most common pollutants from mining activities. Other industrial activities contribute due to the increased need for goods due to population growth.

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Developed countries exhibit high heavy metal contents in suspended solids and sediments where there has been intense industrial activity. In the Rhine River, concentration of cobalt, copper, and cadmium increased from 1900 to the 1970s. Upon realization of the pollution, implementation of new legislation and modification of industrial processes occurred, thus decreasing heavy metal and other elements in the water and sediments during the period of 1975 to 1985. Concentrations of mercury, lead, zinc, copper, and cadmium increased in the Seine River in France (Meybeck, 2001) from upstream to downstream. Rivers contribute significantly to the collection and distribution of contaminants. Farm, industrial, and urban wastes end up in the rivers. The rivers then carry the suspended solids to coastal areas. Most artificial sedimentary reservoirs for contaminant and particle trapping are found in Europe, followed by North America, Africa, and Australia. Atmospheric inputs can also be significant. The wind can carry many pollutants that then fall into water bodies. Nuclear testing and accidents such as the Chernobyl nuclear plant explosion have contributed fallout to nearby and not so nearby regions. Acid rain fallout has also been increasing since the late twentieth century. Estimates are difficult to obtain due to the long-term monitoring requirements and numerical simulations required. Solid or liquid residues have been dumped for many years into the marine environment. Little monitoring was done prior to the 1970s. Dumped materials included building and construction wastes, industrial, farm, and domestic wastes, chemical and radioactive products, and military products (devices, weapons, and explosives). The dumping has been mainly in deep sea areas greater than 1000 m, although dredging materials can be in more shallow zones closer to the shore. Oil spills are well-known environmental risks. They have led to serious pollution problems in the Gulf of Mexico, Alaska, Nova Scotia, and in many regions in the English Channel and North Atlantic coast. Less well known is that any other chemicals such as acids, ammonia, heavy metal, fertilizers, pesticides, and other corrosive materials are also transported, and thus spills along the coasts can impact the environment. Long-term dispersion and fate of these chemicals in a marine environment requires better understanding. Other modes of hydrocarbon transport can be equally or more important than oil spills. Owen et al. (1998) estimated that submarine oil field seepage accounts for 15% of marine pollution, which is three times the amount from oil spills (5%). Other sources include river runoff (41%), tanker dumping or washing (15%), industrial and municipal discharge (11%), coastal refineries and offshore exploration (6.5%), and atmospheric sources (4%). It is likely that offshore exploration will increase due to rising oil prices, and hence the incidences will also become more frequent. Other contaminants include oil and grease, pesticides, insecticides, and microbial agents. In Lake Geneva, highest levels were found in the period from 1960 to 1975 of the hydrocarbons (poly- and hexachlorobenzene) and DDT insecticides (dichlorodiphenyltrichloroethane) and the breakdown products. The same trends have been seen in the sediments of the Great Lakes of North America (Chamley, 2003). However, in developing countries, significant pollution problems are occurring. Pathogens are a major problem. The control of pollution is seen as costly and not a


9

priority in areas where lack of food is a substantial problem. Many wastewater plants also do not disinfect their effluents before discharge. Pathogens are known to concentrate in the sediments. In densely populated areas, reduction of pollutant discharges is the key. Legislative standards have been applied and thus are reducing emissions. The legislation must be implemented and monitored to ensure compliance. However, due to economic pressures on many governments, monitoring is not being strictly carried out. This leaves individuals and enterprises with the responsibility of limiting environmental damage. Treatment of discharges to reduce toxicity and minimization of water through reuse reduces the entry of toxic substances and suspended solids in to the environment. The hydrosphere refers to all the forms of water on Earth (i.e., oceans, rivers, lakes, ponds, wetlands, estuaries, inlets, aquifers, groundwater, coastal waters, snow, ice, etc., as seen in Figure 1.1). The geoenvironment includes all the receiving waters contained within the terra firma in the hydrosphere. This excludes oceans and seas, but includes rivers, lakes, ponds, inlets, wetlands, estuaries, coastal marine waters, groundwater, and aquifers. The marine environment in the geoenvironment is included based on the discharge of pollutants in the coastal regions via runoffs on land and polluted waters from rivers or streams. Microorganisms from agricultural, septic, and sewage discharges are another type of pollutant. They can contribute to the turbidity, odor, and increased oxygen demand in the water. Drinking water contaminated with organisms such as Escherichia coli can lead to severe gastrointestinal diseases and possible death. In a small town 200 km north of Toronto, Ontario, Canada (Walkerton), more than 2300 people became ill, and seven died as the result of drinking water from a well contaminated by surface runoff of manure.

1.4 Management of Contaminated Sediments Dredging of sediments is extensively used for maintenance of rivers, harbors, canals, and other areas to ensure boat navigation. For example, in France more than 19 Mm3 of sediments are dredged to maintain the Seine, Garonne, and Loire estuaries (Chamely, 2003). This activity increases the levels of suspended matter in the water which is subject to transport. In addition, dredged sediments which can contain high levels of contaminants are either landfilled or ocean disposed. Metals, including arsenic, cadmium, copper, mercury, nickel, and lead, PCBs, polycyclic aromatic hydrocarbons (PAHs), pharmaceuticals, and bacterial and viral contaminants are often found in the harbor sediments. Land disposal is similar to the disposal of other wastes. Incineration, confinement, controlled dumping, and chemical stabilization/solidification are some of the processes employed. Transport of the sediments over long distances may also be required. There is also the potential for return of the sediments to the water due to runoff or leaching of the contaminants. Dredging is often delayed due to management problems, but this can lead to further risks. Ocean disposal can lead to the return of the contaminants to the shore if the currents transport them. Often sediment dumping at sea is at shallow depths near the coast zone to reduce cost. Harbor sediments, in particular, can be contaminated. Recently, Sector 103 of the Port of Montreal

10


was dredged to remove the contamination from heavy metals and hydrocarbons. In a Great Lakes harbor, navigational dredging has not been performed since 1972, because there are no economically and environmentally feasible ways to manage the dredged sediment (USACE, 1995). Ships cannot enter the harbor easily, and loading/ unloading is becoming problematic. All of these problems increased transportation costs in the Indiana Harbor Ship Canal and decreased shipping capacity by 15%. Reduction of pollutant release at the source is required to prevent accumulation of the contaminants in sediments from both point and nonpoint sources. Prevention and source control programs are required to ensure this. For example, industrial plants must have adequate treatment and storage systems. Mining is a major source of heavy metal discharges. Domestic and sanitary sources provide organic inputs into the waterways. Agricultural fertilizers should not be overused and should be applied as needed by the plants. Some measures for reduction have been discussed previously (Yong et al., 2006). Water is a major transporter of the contaminants from lakes and rivers into the oceans. In addition, contaminants can be trapped in the sediments of artificial lakes and waterways where natural discharges are not possible. Strict regulations and sediment quality monitoring are required. Inventories of sediment quality are needed. Many have not been updated for many years. As previously discussed, reduction of the inputs can significantly improve sediment quality. One of the key areas of concern for accumulation of contaminants in the food chain has been the Great Lakes area. Many years of industrial and municipal discharges have occurred, but little attention was paid to the state of the bottom sediments until the 1980s. The EPA Great Lakes National Program Office (GLNPO) has indicated that contaminated sediments are the most significant source of contaminants for the food chain in the Great Lakes rivers and harbors. There are 42 Areas of Concern (AOC), and as a result more than 1.8 million cubic m3 have been removed from the Basin from 1997 to 2002 (http://www.epa.gov/glnpo/glindicators/sediments/remediateb.html). In 2004, more than 3,221 advisories for the limitation of fish consumption were issued. More than 35% of the total lake area, 24% of the total river lengths, and 100% of the Great Lakes and connecting waters were covered, mainly because of the contamination of the sediment (USEPA, 2005). Navigational dredging in harbors and ports is often not completed due to the cost and concern for water quality and sediment disposal issues. The Superfund program started to take action regarding about 140 contaminated sediment sites. The most frequently found contaminants were PCBs (44%) and metals (39%), followed by PAHs (24%), mercury (15%), pesticides (12%), and a mixture of others (14%). Much progress has been made in developed countries with regards to recycling and reduction of pollutants at the source. Tools for the evaluation and characterization of contaminants in the sediments will be discussed in a later chapter (Chapter 3). However, in developing countries the challenges are substantial. In the ocean, discharges at sea must be reduced. This can allow the natural purification processes to be exploited. Not only are discharges directly into the sea problematic but incineration of wastes (vinyl chlorides, PCBs) is also practiced (Salomons et al., 1988). Dumping has been regulated since the 1970s and consists of building, construction, and demolition products, industrial, farm, and domestic wastes, and


11

chemical/radioactive wastes. Most authorized disposal areas in deep seas of more than 1000 m in depth are located in the Atlantic Ocean near England, Canada, and the United States. The dispersion of smoke and particles into the atmosphere can potentially occur and lead to fallouts into the oceans. Mercury can accumulate in ocean sediments due to this mechanism. River discharges can carry land particulates to the sea Erosion and dredging can disperse contaminated sediments into previously uncontaminated areas. The effects of dredging need to be minimized and beneficial uses of dredged material promoted as much as possible. Eutrophication from elevated nutrient inputs and bioaccumulation in the food chain disrupt the hydrosphere, biosphere, and lithosphere. Remediation management tools as an alternative to dredging are also required. Monitoring is required to ensure that risk management objectives are achieved and that source control and prevention are carried out adequately.

1.5 Natural Mitigation Processes More recently, the assimilative capacity of sediment materials has been exploited as a means to attenuate the contaminants in the contaminated sediments. The term natural recovery (NR) has been used to identify the results of contamination attenuation in the sediments through natural processes. The processes involved are in almost all respects similar to those available in the corresponding natural attenuation (NA) treatment processes used in the solid land environment and have been described in Yong and Mulligan (2004). The primary processes involved in NR fall under the category of bioremediation or biotransformation. These are complex processes that are not only conditioned by the natural microbial communities and metabolic processes, but also by the nature of the organic compounds and the other sediment components. Natural purification processes include sorption, precipitation, biodegradation, dilution, and dispersion (Figure 1.5). These processes are known as natural attenuation or, in the case of sediments, natural recovery. These will be discussed in more detail in Chapter 5. Contaminants can accumulate for decades due to sedimentation in the bottom of lakes and rivers. The risk of contamination of the water due to propeller and boat movement is increased. During floods, sediment erosion is enhanced. Fluctuating pH conditions also can release poorly bound or unstable fractions of oxides and organic complexes. Natural processes for the reduction of the amounts of contaminants in the sediment have been utilized as a means of purification. Dilution and bacterial activity are the main processes. However, due to excessive pollutant inputs in areas such as the Baltic and Mediterranean Seas (Chamely, 2003), the natural properties of recovery have diminished. In the marine environment in particular, the potential requires much more understanding to assist in long-term management measures. The DDT group of insecticides has been discharged off the California coast since 1970 (Zeng and Venkatesan, 1999). The sediments have shown decreasing levels due to biodegradation and dilution. Additional particle trapping and diffusion outside of the discharge zone may also have occurred. The Great Lakes of North America include Superior, Huron, Michigan, Erie, and Ontario. They are the largest fresh water system in the world (USEPA, 1995). More

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Sediments Contamination and Sustainable Remediation Suspended solids

Sedimenting particles with sorbed pollutants

Land-based and airborne contaminants

Sedimenting particles

Suspended contaminated solids

Benthic boundary layer flow Bioturbation by benthic fauna Chemical exchange across sediment-water interface Mobility & resuspension of contaminants

Benthic-demersal exchange

Sediment

Figure 1.5 Processes contributing to contamination and retention of contaminants in the surface sediment layer.

than 33 million people live near the water. The water is used for consumption, transportation, agriculture, power, recreation, extraction of natural resources, and other uses. Although at one time 180 fish species lived in the Great Lakes, the number has decreased substantially due to pollution and loss of habitat. Contaminated sediments have led to commercial and recreational fishing advisories. Fish tumors and deformities, degradation of phyto- and zooplankton, eutrophication, and the growth of undesired plants have increased, and degradation of aesthetics has been noted. Although impacts must be reduced, sediment remediation has been slow due to a lack of information regarding the sources and extent of the problem and a lack of cost-effective remediation technologies, funding limitations, and political problems. Natural recovery is an attractive solution at many sites in the Great Lakes. Various case studies will be examined in Chapter 5.

1.6 Bioaccumulation of Contaminants As sediments are a reservoir for contaminants, the fish and benthic organisms that live within them can accumulate toxic compounds. The levels can bioaccumulate up the food chain to birds, fish, and other animals to toxic levels. Neurological, developmental, and reproductive problems may manifest. In the United States, the EPA reported that more than 2100 state advisories were issued due to health hazards from consuming fish (USEPA, 1998). Ninety-six watersheds were identified as “areas of probable concern.” Sediment toxicity tests are now used to evaluate sediment contamination.


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The EPA has also proposed that pollution prevention measures should include development of guidelines for new chemicals based on bioavailability and partitioning to sediments. A list of some of the effects of various chemicals is shown in Table 1.1. Sediment Quality guidelines of the Canadian Ministry of the Environment (CCME) are based on the chemical concentration in the sediment that causes an effect on aquatic species (CCME 1999). Two reference values are established, the threshold effect level (TEL) and the probable effect level (PEL). Recently in Quebec, three additional reference values were added, the rare effect concentration (REL), the occasional effect level (OEL) and the frequent effect level (FEL) (Environment Canada and the Ministère de Développement durable, de l’Environnement et des Parcs du Québec, 2008). The two latter effect levels are to be used for management of dredged sediment disposal and remediation decisions. A full list of the assessment quality criteria levels for a wide variety of chemicals is presented in Appendix A for fresh and marine sediments. The guidelines have limitations, including the lack of incorporation of bioaccumulation (accumulation in biological tissues) and biomagnification (accumulation as the concentration goes up the food chain), and the absence of consideration of other effects such as elevated suspended solids levels and loss of habitat. The effect on specific species is not considered, in addition to additive, synergistic, or antagonistic effects. PCBs, pesticides, and methyl mercury are examples of contaminants that both bioaccumulate and biomagnify. Contamination and its linkage to society is complex. Economic development and increasing population put pressure on the environment. How technological developTable 1.1 Chronic Effects of Some Hazardous Wastes Waste Type Pesticides Herbicides (2-4-D* and others) Polychlorinated biphenyls Halogenated organics Nonhalogenated volatile organics Zn, Cu, Se, Cr, Ni, Pb Hg Cd As Cyanides Fecal contaminants

Effect Nervous system, liver, kidney effects, possible carcinogen, mutagen, teratogen Nervous system, liver, kidney effects, possible carcinogen, mutagen, teratogen Potential carcinogen, teratogen Carcinogenic and mutagenic risk Potential carcinogen and mutagen Liver and kidney effects, cancer risk Nervous and kidney effects, mutagenic and teratogenic risk Kidney deficiency, cancer risk Dermal and nervous system toxicity effects, cancer risk Poisoning Potential digestive system risks

Source: Adapted from Governor’s Office of Appropriate Technology, Toxic Waste Assessment Group, California, 1981, adapted from Chamley, 2003. * No reportable information available.

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ment and exploitation of the natural processes can be used to minimize environmental risk will be a subject of this book.

1.7 Sustainable Sediment Management Practices Once sediments are identified as contaminated after an investigation that indicates the potential for risk to human health, fisheries, or the environment, then a remediation methodology must be developed. Strategies for remediation of contaminated sediments must consider the combination of (1) the nature and distribution of the contaminated sediments, (2) determination of the nature, properties, and characteristics of the sediments, (3) development of the necessary remediation treatment technologies that will successfully remove the contaminants from the sediments and minimize risk during and after remediation, and (4) applying the necessary technological evaluation and monitoring to support the decontamination treatment and ensure the sustainability of the remediation. Present remediation procedures tend to either remove the contaminated sediments or employ in situ methods to manage contaminated surface sediments. To a large extent, these methods effectively reduce the bioavailability and transfer of contaminants into the water column. In situ chemical or biological treatment and natural processes can be used. Treatment options of dredged materials should also be considered, particularly to ensure beneficial uses (USACE/USEPA, 2004). This will contribute to the reduction of the use of nonrenewable geological resources. In the 1990s, according to Forstner and Apitz (2007), removal was the main approach utilized in North America and Europe. However, due to the substantial costs for removal of large volumes and the risks to the environment, in situ management approaches are becoming more acceptable. The most common techniques include: • Environmental dredging following by drying and sediment handling • Sediment treatment of dredged materials by physical, chemical, and biological processes • Containment in contained disposal facilities (CDFs), contained aquatic disposal (CAD), and landfills • In situ capping • Monitored Natural Recovery (MNR) • In situ treatments by chemical or biological processes Selection of the most appropriate method is difficult and has been the subject of much discussion. This book will discuss selection criteria and aspects to be considered during the evaluation of the remediation technology. The process of the evaluation will involve the following steps: characterization and assessment of the problem, source control implementation, site and sediment characterization, comparison and assessment of the remediation alternative, selection of the remediation, and determination of the monitoring and management methodology. Knowledge of the nature and composition of contaminated sediment is required to avoid resuspension and remobilization of contaminants. The information obtained will also allow one to


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determine the best or most effective means for treatment for remediation of the contaminated sediment—consistent with cost-effective considerations. Limitations of each alternative will be addressed. Each step of this process will be discussed in this book. Mixtures of heavy metals, hydrocarbons, and chlorohydrocarbons pose substantial challenges. Regulatory standards and criteria must be met. Consultation with the public should be done at all phases. This will enable concerns to be identified and addressed early. Some concerns include (USEPA, 2005): • • • • • • •

Human health impacts Ecological impacts Loss of recreational activities Loss of fisheries, property values, development opportunities, tourism Identification of all contaminants and their sources Loss of commercial navigation Loss of traditional cultural aspects by native tribes

Sustainability is an additional element to be considered in an effort to work toward meeting the goals of sustainability. Resource conservation and management and preservation of diversity are included. If not, the capability of the aquatic geoenvironment to provide the basis of life support will be diminished. To be sustainable, the sediments would need to remain harmless over a long period of time. Ultimately, the habitat should be restored to enable species preservation and biodiversity regeneration. Sustainability, here, refers to the ability of the system to maintain or preserve the initial condition, state, or level before contamination. Sustainability of remediated sediments refers to the ability of the remediated sediments to be preserved in the remediated condition. The key to a sustainability assessment is to minimize and/ or eliminate health threats to humans. Revitalization of land and water areas is another key aspect to be considered in evaluating the sustainability aspects. The use of waterfront properties, harbors, and water bodies can be substantially enhanced and revitalized by sediment decontamination projects. The various aspects of the Lachine Canal project in the Montreal area will be discussed in Chapter 9. Land use plans should be reviewed, and land owners and planning and development agencies should be consulted. For a remediated sediment treatment to become sustainable, (a) the sediment must not require retreatment to maintain its remediated state, and (b) it must reestablish its original uncontaminated benthic ecosystem. Retreatment of contaminated remediated sediments is not desirable for many reasons and needs to be avoided. Information on the sources of contaminants provides the nature and composition of the contaminants. These can be numerous and difficult to identify. They may also lead to diffuse contamination over large areas. Knowledge of the sources of contaminants will provide the means for developing regulations and strategies for managing or controlling the discharge of contaminants that would eventually find their way into the receiving waters and impact the sustainability of any remedial action. The various strategies for remediation of contaminated sediments provide for different results concerning how the contaminants in the sediments are neutralized or eliminated. Some of the remediation techniques available are listed in Figure 1.6.

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Sediment before contamination – i.e. clean sediment with healthy demersal fish, benthic organisms and biodiversity

Dredging of contaminated sediment layer In-situ capping Immobilization of contaminants In-situ chemical and biological treatments

Contaminated Sediment

Remediation Aim Elimination of bioavailability of contaminants

Remediated sediment Re-establishment of habitat and regeneration of biodiversity?

Figure 1.6 Alternatives for remediation of contaminated sediments.

The nature of the remediated sediment will have a direct influence on the strategies and capabilities for sustainability of the remediated sediment to be achieved. These techniques will be examined in later chapters. The requirements for remediated sediment sustainability are controlled by the information from the short- and long-term human health risks, regulatory attitudes and goals, economics, and site specifics. Decision frameworks must be based on a good scientific knowledge of the site. Figure 1.7 shows that the primary source for resuspension and remobilization of contaminants in the sediment is the top portion of the contaminated surface sediment layer. Bioturbation and benthic boundary layer flow, including tidal exchange, will most likely affect only about the top 30 cm of the surface sediment layer. This figure shows some of the difficulties of remediating sediment sites. These natural forces influence contaminant transport.

1.8 Concluding Remarks Proper management of the aquatic geoenvironment is needed to protect future generations, but is highly complex. Water quality must not be degraded so that it cannot be consumed without risk to the health. The same follows for all resources obtained from the water. Sediment as a natural resource must not be depleted through quality degradation. Technologies for environmental management for remediation and impact avoidance would reduce the degradation of sediment quality and will be examined thoroughly in the following chapters. Protocols and procedures to monitor and manage changes in the environment will also be required and will be discussed in this book.

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Leaching

Settling

Predators-Birds and fish

Resuspension

Microbes/benthos

Sediment

Figure 1.7 Interactions of abiotic and biotic elements.

Obtaining sustainable remediated sediment requires (a) source control of contaminants entering the ecosystem, (b) natural processes within the surface sediment layer that maintains the remediated state of the sediment, and (c) restoration of habitat and reestablishment of biodiversity. Human intervention in providing the necessary elements for restoration of habitat and reestablishment of biodiversity, after or during remediation of the contaminated sediment, will provide for sustainable remediated sediment. However, it must be done in a cost-effective manner.

References Birch, G. and Taylor, S. 1999. Source of heavy metals in sediment of the Port Jackson estuary, Australia. Sci. Total Environ. 227: 123–138. Brils, J.M. 2003. The SedNet Strategy Paper: The opinion of SedNet on environmentally, socially and economically viable sediment management. SedNet. http://www.SedNet.org. CCME 1999. Canadian Sediment Quality Guidelines for the Protection of Aquatic Life. Canadian Council of Ministers of the Environment. CCME EPC-98E http://www.ccme. ca/assets/pdf/sedqg_protocol.pdf. Chamley, H. 2003. Geosciences, Environment and Man. Elsevier, Amsterdam. Environment Canada and Ministère du Développement durable, de l’Environnement et des Parcs du Québec. 2008. Criteria for the Assessment of Sediment Quality in Quebec and Application Frameworks: Prevention, Dredging and Remediation. FÖrstner, U. and Apitz, S.E. 2007. State of the art in the USA. Sediment remediation: U.S. focus on capping and monitored natural recovery. J. Soil Sediments, 7(6): 351–358. Inoue, T., Mulligan, C.N., Zadeh, E.M. and Fukue, M. 2009. Effect of contaminated suspended solids on water and sediment qualities and their treatment. J. ASTM International. 6(3), pages 1–11, Paper ID JAI102185. Meybeck, M. 2001. Transport et qualité des sediments fluviaux: Variabilités temporelle et spatiale, enjeux de gestions. Publication de la Société Hydrotechnique de France. 166th sess, 11–27. Owen, O.S., Chiras, D.D. and Reganold, J.P. 1998. Natural Resource Conservation. 7th ed. Prentice Hall, 594p.

18


Salomons, W., Bayne, B., Duursma, E.K. and Forstner, U. 1988. Pollution of the North Sea: An Assessment. Springer, Berlin. Trevors, J.T. 2003. Editorial: biodiversity and environmental pollution. Water, Air Soil Pollut. 150:1–2. USACE 1995. Ecosystem Restoration in the Civil Works Program. ER-1105-2-210. USACE (U.S. Army Corps of Engineers), Washington, DC. USACE/USEPA 2004. Evaluating environmental effects of dredged material management alternatives—A technical framework. EPA 842-B-92-008, U.S. Army Corps of Engineers and U.S. Environmental Protection Agency. Washington, DC. USEPA 1995. Water quality guidance for the Great Lakes system. USEPA. Federal Register 60: 15366-153425. USEPA 1998. EPA’s Contaminated Sediment Management Strategy. EPA-823-R-98-001, United States Environmental Protection Agency, Office of Water, Washington, DC. USEPA 2002. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. United States Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC. Report for OSWER 9355.0-85. USEPA 2005. Contaminated Sediment Remediation Guidance for Hazardous Waste Sites. Environmental Protection Agency, Office of Solid Wastes and Emergency Response, EPA-540-R-05-012, OSWER 9355.0-85, Washington, DC. Varanasi, U., Casillas, E., Arkoosh, M.R., Hom, T., Misitano, D.A., Brown, D.W., Chan, S.-L., Collier, T.K., McCain, B.B., and Stein, J.E. 1993. Contaminant exposure and associated biological effects in juvenile Chinook salmon (Oncorrhyncus tshawytscha) from urban and nonurban estuaries of Puget Sound, Seattle, WA. National Oceanic and Atmospheric Administration (NOAA) National Marine Fisheries Service, NMFS NWFSC-8. WHO 1999. Toxic Cyanobacteria in Water: A Guide to Their Public Health Consequences, Monitoring. Chorus, I. and Bartram, J. (Eds.). W& FN Spon, London and New York. Yong, R.N. 2001. Geoenvironmental Engineering: Contaminated Soils, Pollutant Fate and Mitigation. CRC Press, Boca Raton, FL. Yong, R.N. and Mulligan, C.N. 2004. Natural Attenuation of Contaminants in Soils. CRC Press, Boca Raton, FL. Yong, R.N., Mulligan, C.N., and Fukue, M. 2006. Geoenvironmental Sustainability. CRC Press, Boca Raton, FL. 387 pp. Zeng, E.Y. and Venkatesan, M.I. 1999. Dispersion of sediment DDTs in the coastal ocean off southern California. Sci. Total Environ. 229: 195–208.

2 Introduction to Sediments 2.1 Introduction Parent rock can be broken down by physical and chemical weathering. Weathered rocks, such as coarse grains and clay minerals, are transported by the flow of water and are deposited in rivers, lakes, estuaries, and sea areas. These materials form the sediments in water. On the other hand, smaller particles and materials dispersed from volcanoes and transported by the wind are called aeolian soil upon deposit. Soil organic matter degraded by microbial activities is also discharged into rivers, lakes, estuaries, and sea areas with inorganic particles. Furthermore, a variety of substances are discharged through human activities. These are fed into water through various channels. Thus, sediments are in contact with inorganic, organic, and other human-discharged materials, through the influence of the pore water. Therefore, the properties of the pore water are an important factor regarding the quality of the sediments. Since the industrial revolution, around 1750, a variety of production and consumption activities by humans have also created problems associated with waste materials, because some of the wastes which have been discharged and have accumulated are hazardous or toxic (Cappuyns et al., 2006; Fabris et al., 1999; Fukue et al., 2007). Fine particles discharged from land that are easily suspended in water are called “suspended solids.” They can agglomerate in the water and start settling. Generally, these particles consist of many fine materials such as clay minerals, organic matter (including plankton), oxides and hydroxides, etc. They often adsorb nutrients and hazardous substances, in addition to bacteria and viruses. Figure 2.1 shows an example of settling particles in a brackish lake. There are basically two types of problems related to sediments: eutrophication with nutrients and contamination with hazardous and toxic substances. Basically, the adsorption and desorption of contaminants and the degradation of organic particles can become problematic. Eutrophication and contamination cannot be treated in the same way, because contaminants are hazardous, whereas nutrients are not. Sediments are often called “mud,” “sand,” and “gravel,” depending on the nature of the deposited materials. In fact, this classification has been used for anchoring ships, and the terms are indicated in the chart. Although these names are mostly due to the size of sediment particles, they are only generic names. For example, when sediments are organic rich, or smaller particles, they are often called “mud.” However, there are detailed classification methods for sediments for scientific and engineering purposes. Sediments are often called marine soils or lake soils. They are also called marinedeposited soils or lake-deposited soils. These are all contained in the categories of 19

20


Figure 2.1 Settling particles in a brackish lake.

sediments. Therefore, sediments are defined as any solid deposited at the bottom of a ditch, river, lake, or sea. Accordingly, they are called ditch sediments, river sediments, lake sediments, or marine sediments, respectively. They can also be separated into fresh and marine sediments. The intermediate sediments are sometimes called brackish sediments. From an environmental point of view, sediments in fresh water are distinguished from sediments in seawater because of the different associated food chains and biological concentrations. For example, Canadian guidelines provide more severe values for the guidelines for marine sediments than for freshwater sediments. In coastal regions, the origin of sediments is mostly the land. However, a portion of the sediments is produced in water. They are of plankton, authigenic minerals, crusts, aquatic plants, or other organic origins. Some of these products are buried with deposits from land, and therefore, the ratio of marine produced to discharged materials from land is lower near the coasts, but will increase with distance from the coast. At ocean bottoms far from the coast, the effect of land materials is small, and thus the sediments consist mainly of products formed under marine conditions. A typical example is ooze (Wetzel, 1989). Wetzel (1989) investigated the consolidation of ooze in deep ocean. Diagenesis that occurred there formed chalk and sedimentary limestone layers. In general, larger discharged solid particles are transported near the shore and bottom by water currents and waves, whereas finer particles will disperse further. They finally settle on the bottom but can move again, depending on the water action. In this sense, surface sediments are more active than the underlying sediments. Therefore, erosion is dependent on the balance of the settlement and movement of the sediments. Thus, the reduction in the discharge can cause coastal erosion. In many cases, the control of soil discharge in mountainous regions has caused coastal erosion.

21

Introduction to Sediments

×1,000

10 µm

Figure 2.2 Pyrites formed in marine sediments.

New minerals can form in sediments due to the change in reduction-oxidation conditions. Pyrite is a typical product formed under marine reduced conditions. If pyrite is found in sediments (Figure 2.2), it means that there is a lack of dissolved oxygen and a low reduction-oxidation (redox) potential.

2.2 Definition of Sediments In this book, sediments are defined as solids that have settled and deposited at the bottom of the water column. They contain liquid and gas phases, which is similar to the definition of soil in geotechnical engineering. Therefore, sediments consist of sediment particles (solid), pore water (liquid), and gas. The liquid may be fresh water, seawater, wastewater, or a mixture of them. The gas may be air, methane, another type of gas, or a mixture of gases. In this sense, marine-deposited soils and fluvial sediments can be classified as sediments. However, problems with those sediments have often been dealt with in a manner similar to soil and groundwater, because they have required different approaches from sediments under water. Therefore, sediments within groundwater are distinguished from the sediments under surface water in this book.

2.3 Types of Sediments There are some classification methods corresponding to the objectives. Therefore, the type of sediment depends on the methods of classification. The determination of the classification of sediments requires some testing and/or analyses. Since the quality of sediments can be obtained by evaluating the properties, the selection of test methods and analyses is important. Sediments can be primarily classified into three categories (i.e., marine, fresh, and brackish sediments). The term brackish is mainly associated with the water

22


fraction, not the sediment. The word brackish comes from the Middle Dutch root “brak” which means salten or salty. Usually, brackish is used for water having a salt concentration greater than 0.5 up to 30 parts per thousand (ppt), whereas seawater has a concentration between 30 and 50 ppt. The Baltic Sea is a brackish sea adjoining the North Sea. Initially, prior to the Pleistocene epoch two major river systems met at this location. However, although it was flooded by the North Sea, it still receives a sufficient quantity of fresh water from the adjacent lands that makes the water brackish (http://en.wikipedia.org/wiki/ Brackish_water#Brackish_seas_and_lakes). There are many brackish lakes and rivers that are connected to the sea. Estuaries are where seawater and fresh water mix, and consequently they are under brackish conditions.

2.3.1 Types of Sediments by Components Sediments are composed of various components, as shown in Figure 2.3. Solids in the sediments include organic and inorganic particles. In general, organic particles have lower specific gravities than that of inorganic particles. If a sediment has a specific gravity lower than 2.5, it usually contains an ignition loss greater than 15%. This is compared to the typical value of 2.65 for primary minerals, such as feldspar and quartz. Sediments are evaluated according to the organic matter content. If the ignition loss or total organic carbon is high, the sediment is called organic sediment or sediment with organic matter. Sediment

Solid Particles

Inorganic

Gas

Pore Water

Organic

Crystalline Primary Minerals, Clay Minerals Carbonates, Sulfates Non-crystalline (amorphous) Allophanes, Oxides, Hydroxides

Fresh Water

Humic Acid

Sea Water

Fulvic Acid

Dissolved Components

Degraded Materials Humins, Lignins

Peptides, Lipids, Carbohydrates

Figure 2.3 Various components of sediments.

Air, Methane, Hydrogen Sulfides

23

Introduction to Sediments

Pore water can include fresh water, seawater, or other liquids like wastewater. The quality of the pore water is very important from an environmental point of view, because it affects aquatic life. The quality of the pore water can be analyzed with chemical procedures using appropriate sampling techniques. Pore gas can also be important in characterizing some types of sediments, because anaerobic conditions will produce methane gas and hydrogen sulfide. The existence of CO2 is also possible. Figure 2.4 shows the solid phase of the sediments for both the inorganic and organic components. The inorganic components can be crystalline or noncrystalline. More detail can be found in Yong and Mulligan (2004), but briefly they can be described as in the sections that follow. 2.3.1.1 Primary Minerals Primary minerals are derived from the parent rock material through mainly physical weathering processes. Primary minerals include quartz, feldspar, micas, amphiboles, and pyroxenes and are generally found as sand and silt fractions. However, quartz is chemically stable and exists as a small portion of clay-sized fractions. 2.3.1.2 Secondary Minerals Secondary minerals are formed by physical, chemical, and/or biological weathering processes. These minerals are layer silicates and are known as phyllosilicates. They comprise a major fraction of the clay-sized materials in clays. Clays and clay soils refer to soils that have particle sizes less than 2 micron effective diameter (draft by ISO). However, some countries like the United States use different definitions for clay fractions (i.e., Fe3+ > Al3+ > Cu2+ > Ba2+ > Ca2+ = Mg2+ > Cs+ > K+ = NH4+ > Li+> Na+ Exchange-equilibrium equations can be used to determine the proportion of each exchangeable cation to the total cation exchange capacity (CEC) as the outside ion concentration varies. The simplest is the Gapon relationship: 1

 M om+  m M em+ = K 1 N en+  N on+  n

(3.5)

where m and n refer to the valence of the cations, and the subscripts e and o refer to the exchangeable and bulk solution ions, respectively. The constant K is dependent on the effects of specific cation adsorption and the nature of the clay surface. K decreases in value as the surface density of charges increases. The adsorption of ions due to the mechanism of electrostatic bonding is called physical adsorption or nonspecific adsorption. The surface properties of sediments are important, because it is these properties, together with those surface properties of pollutants themselves and the geometry and

Contaminant–Sediment Interactions

41

continuity of the pore spaces that will control the transport processes of the pollutants. The sediment fractions that possess significant reactive surfaces include layer silicates (clay minerals), organic matter, hydrous oxides, carbonates, and sulfates. The surface hydroxyls (OH– group) are the most common surface functional group in inorganic sediment particles such as clay minerals with disrupted layers (e.g., broken crystallites), hydrous oxides, and amorphous silicate minerals. The common functional groups for organic matter include the hydroxyl, carboxyl, and phenolic groups and amines.

3.3 Sorption of Pollutants and Partition Coefficients The processes of transfer of metal cations from the sediment pore water can be grouped as follows. Sorption includes physical adsorption (physisorption), occurring principally as a result of ion exchange reactions and van der Waals forces, and chemical adsorption (chemisorption), which involves short-range chemical valence bonds as previously discussed. The term sorption is used to indicate the process in which the solutes (ions, molecules, and compounds) are partitioned between the liquid phase and the particle interface. As it is difficult to fully distinguish between the mechanisms of physical adsorption, chemical adsorption, and precipitation, the term sorption is used. Physical adsorption occurs when the pollutants or contaminants in the solution (aqueous phase, pore water) are attracted to the surfaces of the sediment particles because of the unsatisfied charges. In the case of the heavy metals (metal cations) for example, they are attracted to the negative charges exhibited by the surfaces of the particle solids. This sorption is a function of pH. For example, Fe(OH)3, a major soil component, has a variable charge with pH. The pH of the zero charge point for this component, where the positive and negative charges are equal, is 8.5. Below that pH, cationic species would be unlikely to sorb onto the cationic surface. In the case of heavy metals, precipitation of the heavy metals will also remove the heavy metals from solution. Precipitation mechanisms for organic chemical pollutants usually do not occur, so it is generally assumed that the total “partitioned” organic chemicals are sorbed or attached to the solids. The partitioning or distribution of the organic chemical pollutants is described by a coefficient identified as kd. As defined previously, this coefficient refers to the ratio of the concentration of pollutants “held” by the sediment fractions to the concentration of pollutants “remaining” in the pore water (aqueous phase), i.e., Cs =kdCw, where Cs refers to the concentration of the organic pollutants sorbed by the sediment fractions, and Cw refers to the concentration remaining in the aqueous phase (pore water), respectively. Therefore, sediment chemistry and surface characteristics, redox potential, pH, and speciation of the contaminant will all influence sorption. The equilibrium partitioning of pollutants refers to the steady state of transfer of organic pollutants from the pore water to the sediment solids or the reverse, where there is desorption of the pollutant from the sediment particles by processes that include all of those previously described. Organic matter in the pore water and adsorbed onto the sediments can play a significant role. Determination of partitioning of inorganic contaminants and pollutants is generally conducted using batch equilibrium tests. Results obtained from the tests are called adsorption isotherms.

42


Concentration of Target Pollutants Sorbed, c*

Infinite capacity–linear sorption Common type of adsorption isotherm

Slope

= kd

Infinite capacity -- low sorption Equilibrium Concentration of Target Pollutants in Porewater, c

Figure 3.3 Partitioning of pollutants between the pore water and pollutants sorbed by sediment particles.

The three common types of adsorption isotherms (Freundlich, Langmuir, and constant) are shown in Figure 3.3. The parameter kd in the equations shown with the various curves denotes the slope of the curves. Organic matter exists as dissolved and suspended forms and on the bottom sediments. The functional groups of the organic matter interact with heavy metals. The affinities of these groups for heavy metals in decreasing order are: enolates > amines > azo compounds > ring N > carboxylates > ethers > carbonyls On the other hand, organic matter may lead to the extraction of the heavy metals via mineral dissolution and solubilization of metal sulfides and carbonates. The factors of pH, alkalinity, redox potential, and amount of organic matter can all influence the sorption of heavy metals (USEPA, 2005). High levels of Ca, Na, Mg, and K may also decrease heavy metal sorption. Volatilization may be an important attenuation mechanism for volatile organic contaminants. Freshly spilled petroleum products such as gasoline can exhibit high rates of volatilization that can occur from the free phase or dissolved phase. Henry’s constant law describes volatilization from the dissolved phase. The rate of volatilization slows as the age of the spill increases. As a general guideline, a dimensionless Henry’s constant greater than 0.05 means that volatilization or off-gassing is likely, while if it is less than 0.05, volatilization would be negligible. In sediments, this mechanism is not a dominant one due to the depth of the sediments in the water column. However, some components such as mercury can be subjected to volatilization from the surface water (Morel et al., 1998). In lakes, sedimentation and volatilization are major mechanisms of mercury loss, while a number of biochemical and chemical reactions can occur in oceans. Precipitation–volatilization and oxidation–reduction

43

Contaminant–Sediment Interactions Volatilization Water Surface

MeHg

Deposition and dissolution

CH3HgOH Cells CH3HgCl

HgOrg Hg(OH)2 HgClOH HgCln(n–2)– HgCl2

Oxic

Hg(II)

Hg°

Suboxic Anoxic

MeHg

Sediment Surface

SRB

HgOrg, HgS(HS)– HgS(HS)2 Hg(Sn)HS–

Hg(II)

Hg°

Hg precipitation as HgS

Figure 3.4 Mechanisms of Hg conversion in surface water. SRB = sulfate-reducing bacteria. (Adapted from Morel et al., 1998).

reactions function in the mercury cycle. Due to atmospheric inputs of mercury, levels in the sediment have accumulated over the past 150 years (Mason et al., 1994). The forms of Hg can be seen in Figure 3.4. There is elemental mercury, which is volatile but relatively stable, and various mercury species. Near the air–water interface, Hg dominates, whereas total Hg and methyl mercury dominate near the sediments. Total mercury includes particulate and soluble species. Chemical mass transfer is responsible for partitioning of contaminants in the fate and transport of contaminants. Reduction–oxidation reactions can also play an important role in the fate of the contaminants. Assessment of the retention or retardation processes is required to understand partitioning and the attenuation of contaminants within the sediment. If potential pollution hazards and threats to public health and the environment are to be minimized or avoided, we must ensure that the processes for contaminant attenuation are irreversible and the levels of contaminants are below allowable limits or levels. For example, for arsenic, two models exist in respect to possible mechanisms for release of arsenic from the arsenic-bearing materials, as shown in Figure 3.5: (a) reduction mechanisms and (b) oxidation processes. In the former process, it is reasoned that reductive dissolution of arseniferrous iron oxyhydroxides releases the arsenic responsible for pollution of the groundwater. The other model for arsenic release from the alluvium relies on oxidation of the arsenopyrites as the principal mechanism. This occurs when oxygen invades the groundwater because of the lowering of the groundwater from the abstracting tubewells. The sorption of arsenic (III)

44


Sedimentation of As(V)

O2–

Water Surface

Fe(II) oxidation

As(V) on hydroxides

As(V)

As(III)

on FeS

As precipitation sorption

FeCO3

Suboxic Anoxic

As2S3

H2S

Oxic

Fe(II)

Fe(II)

SO42–

Fe(III)

Diffusion

As(III)

Contaminant partitioning

FeS, FeS2 + H2S As(V)/As(III) redox reactions

Electron transfer

Figure 3.5 Mechanisms of As conversion in surface water (adapted from Bostick et al., 2004).

by anoxic estuarine sediments has been studied by Bostick et al. (2004). Although sorption was apparent at all pH values, it was more significant at pH 7. Sorption conformed to Langmuir isotherms. Iron sulfide fractions were responsible for most of the sorption. In addition, over time, the FeAsS-like precipitates reacted to form As2S3 and, when combined with the drop in redox potential, stabilized the arsenic. The sorbed species of arsenic were determined by extended X-ray absorption fine structure (EXAFS) spectroscopy. The organic matter of sediments may change in structure, thus binding metals and other chemicals more tightly (Pignatello et al., 1993). Contaminants such as heavy metals may diffuse into the sediment structure and thus may be tightly bound as well (Steinberg et al., 1987). Petroleum compounds over time lose the more soluble and volatile components (Wilcock et al., 1996) and are thus less bioavailable and less biodegradable (Sandoli et al., 1996).

3.3.1 Partitioning of Inorganic Pollutants Partitioning of inorganic and organic chemical pollutants is often represented by the partition coefficient kp. In brief, partition coefficients describe the relationship between the amount of pollutants transferred onto sediment particles and the equilibrium concentration of the same pollutants remaining in the pore water (Figure 3.6). The popular relationships such as Langmuir and Freundlich are shown. Partitioning is the result of mass transfer of pollutants from the pore water. There are at least two broad issues regarding the determination and use of the distribution coefficient kd , namely: (a) types of tests used to provide information for determination of kd and (b)

45


k 3s s* = 1 + k 4s

Langmuir type

=k

2s m

Freundlich type

s*

Concentration of Solutes Sorbed, s*

High affinity type

s*

=k

s

kn and m are constants, n = 1 to 4

1

Linear adsorption Equilibrium Concentration of Solutes in Solution, s

Figure 3.6 Different types of adsorption isotherms obtained from batch equilibrium tests.

range of applicability of kd in transport and fate predictions. Laboratory tests used to provide information on the mass transfer of pollutants from the pore water onto sediment solids are the most expedient means to provide one with information on the partitioning of pollutants. By and large, these tests provide only the end result of the mass transfer, and not direct information on the basic mechanisms responsible for partitioning. The distribution coefficient kd is determined from information gained using batch equilibrium tests on sediment solutions. Ratios of 10 or 20 parts of solution to one part sediment are generally used, and the candidate or target pollutant is part of the aqueous phase of the sediment solution. In many laboratory test procedures, the candidate sediment is used for the solid in solution, and the candidate or target pollutant is generally a laboratory-prepared pollutant, such as PbNO3 for assessment of sorption of Pb as a pollutant heavy metal. Since the sediment particles are in a highly dispersed state in the slurry, the surfaces of all the particles are available for interaction with the target pollutant in the aqueous phase of the solution. By using multiple batches of sediment solution where the concentration of the target pollutant is varied, and by determining the concentration of pollutants sorbed onto the sediment solids and remaining in the aqueous phase, the characteristic adsorption isotherm curve is obtained, and the slope is defined as kd as shown in Figure 3.6. Distribution coefficients kd obtained from adsorption isotherms using the batch equilibrium with sediment solutions and prepared target pollutants are very useful in that they define the upper limit of partitioning of the target pollutant.

46


The aging or changes over time of the sediments and/or contaminants is referred to as weathering. The dissolution of metal sulfides can release metals such as zinc and lead into the environment. Temperature, surface area of the solids, pH, particle size distribution, oxygen levels, the water flow rate, and ionic strength can all influence weathering rates. Bentley et al. (2006) showed that laboratory column studies could be used to relate the lab studies to field dissolution rates. Scale factors are needed to predict and relate bulk physicochemical lab and field sites. These types of information are important for evaluating metal release from dredged sediments and movement of sediments in the water column. For assessment of partitioning using sediments in their natural state, it is necessary to conduct column-leaching or cell-diffusion tests. In these kinds of tests, the natural sediment is used in the test cell or column, and either laboratory-prepared candidate pollutants or natural leachates are used. The partition coefficient deduced from the test results is not the distribution coefficient identified with the adsorption isotherms obtained from batch equilibrium tests. Instead, the partition coefficients obtained from column-leaching or cell-diffusion tests need to be properly differentiated from the traditional kd. Yong (2001) suggested that these partition coefficients be called sorption coefficients to reflect the sorption performance of the soils in their natural state in the column or cell. The disadvantages in conducting column-leaching and cell-diffusion tests are (a) the greater amount of effort required to conduct the tests, (b) the much greater length of time taken to obtain an entire suite of results, and (c) inability to obtain exact replicate soil structures in the companion columns or cells. The results indicate that the characteristic curves obtained from column-leaching tests, for example, are much lower than corresponding adsorption isotherms. Figure 3.7 gives an example of an experimental setup to perform these tests.

Figure 3.7 Leaching column setup.

47

Contaminant–Sediment Interactions Sequential Removal

Sequential Extraction

Slurry

Centrifuge

Supernatant for analysis of metals

Figure 3.8 Methodology for SSE tests.

3.3.2 Selective Sequential Extraction Measurement of the mobility and availability of metals is required to predict and interpret their behavior. As total metal concentrations do not give a good indication of metal toxicity, other methods are needed. Trace metals can be found in numerous sediment and soil components in different ways (Krishnamurthy et al., 1995). Metals in river sediments can be bound to different compartments: adsorbed onto clay surfaces or iron and manganese oxyhydroxides; present in the lattice of secondary minerals like carbonates, sulfates, or oxides; attached to amorphous materials such as iron and manganese oxyhydroxides; and complexed with organic matter or in the lattice of primary minerals such as silicates (Gismera et al., 2004; Schramel et al., 2000; Tessier et al., 1979). To determine the fractionation of metals in soils, various methods are used. One method is to use specific extractants called selective sequential extraction. By sequentially extracting with solutions of increasing strength, a more precise evaluation of the different fractions can be obtained (Tessier et al., 1982). A soil or sediment sample is shaken over time with a weak extractant and centrifuged, and the supernatant is removed by decantation (Figure 3.8). The pellet is washed in water, and the supernatant is removed and combined with the previous supernatant. A sequence of reagents is used following the same procedure until, finally, mineral acid is used to extract the residual fraction. Heavy metal concentrations are then determined in the various extracts by atomic absorption, inductively coupled plasma (ICP), or other means. Numerous techniques and reagents have been developed and have been applied to soils (Shuman, 1985), sediments (Tessier et al., 1982), sludge-treated soils (Petrozelli et al., 1983), and sludges. Although none of the extractions is completely specific, the extractants are chosen to minimize solubilization of other fractions and provide a distribution of the partitioning of the heavy metals. The extracting agents increase in strength throughout the sequence to destroy the bonds of the heavy metals to the various sediment components of increasing strength (Yong, 2001). As an example, Koeckritz et al. (2001) proposed an equivalent step to simplify the sequential extraction procedure designed

48


by Zeien and Brummer (1989). They reduced four initial steps in the procedure to one with no significant change in the results. Ammonium acetate, barium chloride, or magnesium chloride at pH 7.0 is generally used to extract the exchangeable fraction by displacement of the ions in the sediment matrix bound by electrostatic attraction (Lake, 1987). Calcium chloride, potassium nitrate, and sodium nitrate can also be used (Yong, 2001). Hydroxylamine hydrochloride with acetic acid at pH 2.0 reduces the ferrous and manganese hydroxides (reducible phase) to soluble forms (Tessier et al., 1979). The carbonate phase (calcite and dolomite) is extracted at pH 5.0 with sodium acetate acidified with acetic acid by solubilization of the carbonates, releasing the carbonate-entrapped metals (Yong and Mulligan, 2004). Hot hydrogen peroxide in nitric acid is used to oxidize the organic matter, thus releasing the metals that are complexed, adsorbed, and chelated. The silicates should not be affected by this treatment (Yong, 2001). In the final step, strong acids at high temperatures dissolve the silicates and other materials. This residual fraction is usually used to complete the mass balances for the metals. Yong et al. (1999) reported that, through selective sequential extraction techniques (SSE) described in Table 3.2, the strength of retention mechanisms of heavy metals by the phases of solids decreased in the following order:

carbonates > amorphous > organics > exchangeable

Ho and Evans (2000) investigated the mobility of heavy metals through SSE methods with assessment of readsorption effects. The study showed that Cd was highly mobile, Cu and Pb were associated primarily with oxidizable organic matter, and Zn was found in all fractions. Chartier et al. (2001) indicated that 18% to 42% of Pb, Zn, and Cd exist in the carbonate-bound fraction, while 39% to 60% of these metals were associated with the iron and manganese oxide bound fraction. The study also showed that 65% to 72% of total copper present in the sediments was found in organic matter and sulfide bound fractions; 50% to 80% of Ni and Cr in sediment exist in the residual fraction. Table 3.2 Reagents Used for Sequential Extraction Procedure Chemical Reagents 1 2 3 4 5 6

Water or surfactant MgCl2 (pH 7) NaOAc (pH 5 with acetic acid) NH2OH·HCl in 25% (v/v) acetic acid (pH 2.5) HNO3 and 30% H2O2 (pH 2), 30% H2O2 (pH 2) NH4OAc in 20% (v/v) HNO3 Aqua regia (HCl, HNO3, and water)

Note: Ac—denotes acetate.

Fraction Soluble Exchangeable Carbonates Oxides and hydroxides Organic matter Residual

49


Table 3.3 Sequential Extraction of Metals for Two Sediment Samples Fraction (% Of Total ) Metal Lachine Canal Copper Nickel Zinc Lake Sanaru Copper Lead Zinc

Exchangeable

Carbonate

Oxide

Organic

Residual

1 0 4

1 9 18

4 23 46

86 29 22

12 39 10

Hc). This indicates that, if there is no adsorption in the cap layer, the Cap Drained pore water Hc S

H

pw

Contaminated sediment

Initial

Hc

H´

At the end of consolidation

Figure 6.3 Illustration of advection flow due to consolidation under the load of a cap.

142


0

2

4

6

8

10

0

e = 8.9

10

10 e = 6.8

20

Depth (cm)

30 e = 4.9 40

e = 4.7

Depth (cm)

20 e = 5.5

30 40

Effective Pressure, σv (kPa) 100 200 300

400

50

50 60

0

Contaminated Layer 46.5 cm

Void Ratio, e 0

e = 3.8

60 70

70

Figure 6.4 Measured void ratio profile and calculated effective stress for a soft lake sediment.

contaminants will be released into the water over a long period of time. This may be more dangerous than in the case of no cap, because the advective flow is very low without consolidation due to capping. Some researchers showed that a good cap thickness was approximately 50 cm. However, it may depend on the consolidation characteristics of the sediments, the bulk density of the sand cap, and the type and concentration of the contaminants. Some contaminants are strongly adsorbed to sediment particles (clay particles), and they are not easily released. On the other hand, the degradation of organic matter releases contaminants into the pore water. Furthermore, organic matter contains high amounts of nutrients. Thus, the pore water can be squeezed through the sand cap. If the level of the released substances is predicted to be too high, other techniques, such as an adsorbent or active mat, should be selected. 6.2.2.1 Contaminant Transport The contaminant fluxes can be calculated from the beginning of the release until a maximum concentration is obtained in the overlying water using the following equation,

J = −D

dC dt

(6.14)

where J is the flux, dC/dt the concentration gradient as a function of time, and D is the molecular diffusion coefficient. To ensure the short- and long-term effectiveness of the cap, monitoring is required. This will include evaluation of the integrity of the

10 20 30 40 50 60 Total

Depth (cm)

10 20 30 40 50 60 Total

Depth (cm)

0.1 0.1 0.1 0.1 0.1 0.1

Layer (m)

0.1 0.1 0.1 0.1 0.1 0.1

Layer (m)

8.9 6.8 5.5 4.9 4.7 3.8

Void Ratio

8.9 6.8 5.5 4.9 4.7 3.8

Void Ratio

4.536 3.402 2.7 2.376 2.268 1.782

Cc

4.536 3.402 2.7 2.376 2.268 1.782

Cc 60 125 195 240 280 320

σv′ (kPa)

0.05 0.04 0.04 0.04 0.04 0.04

Cc/ (1+e0)H 60 125 195 240 280 320

σv′ (kPa)

60 cm Sand Caps

0.05 0.04 0.04 0.04 0.04 0.04

Cc/ (1+e0)H

30 cm Sand Caps

3528 3528 3528 3528 3528 3528

σc′ (60 cm) (kPa)

1764 1764 1764 1764 1764 1764

σc′ (30 cm) (kPa)

1.777 1.466 1.281 1.196 1.134 1.080

log (∆σc′/ σv′)

1.483 1.179 1.002 0.922 0.863 0.814

log (∆σc′/ σv′)

0.08 0.06 0.05 0.05 0.05 0.04 0.29

S (m)

0.07 0.05 0.04 0.04 0.03 0.03 0.23

S (m)

pw (m)

0.73 n = 0.4

pw (m)

0.58 n = 0.4

Table 6.1 Calculated Results of Settlement and pw for Lake Sediments under 30- and 60-cm Sand Caps

In Situ Remediation and Management of Contaminated Sediments 143

144


cap through monitoring of the material quality, the thickness of the cap material, and erosion of the cap through resuspension or displacement. Verification must be made particularly after storm events that could have a severe impact on the structure of the cap. It must also be assured that the contaminants are physically isolated by a bathymetric survey, that there is no evidence of chemical diffusion or transport, and that benthic biological recovery is occurring. In other words, the main objectives of the cap must be ensured and determined through monitoring. These are to reduce contaminant fluxes through the cap and to avoid surface sediment and water recontamination. Recovery of the benthic community is another aspect that must be ensured and evaluated during monitoring. Full recovery has been noted at large sites five to seven years after capping (USEPA, 2005).

6.2.3 Active Capping Other active capping approaches have been used to enhance the reduction of contaminant toxicity and mobility. Reactive caps have shown promise. Organoclays, activated carbon, and apatite have been evaluated (FÖrstner and Apitz, 2007). Reactive mats with two geotextiles and reactive materials to bind contaminants are also being developed. A project was carried out by the EPA at the Anacostia River in Maryland (www. ert2.org/sedimentremedy). The sediments contain heavy metals, polycyclic chlorinated biphenyls (PCBs), hydrocarbons, and chlordane. Nearby military and industrial activity were the likely sources of the contaminants. Three active materials, Aquablock™, coke breeze, and apatite, were evaluated as capping materials. Physical, chemical, and biological monitoring was used to evaluate the performance of the caps. Aquablock was effective in terms of physical stability, chemical migration, hydraulic seepage prevention, and effect on flora/fauna such as worms over a 30-month period.

6.3 Rehabilitation of the Coastal Marine Environment Because of anthropogenic activities, the coastal marine environment has changed. Many sand beaches have been lost by the reclamation from sea and erosion. Many coastlines have eroded due to a lower supply of sand from river mouths. Since sand beaches have a natural purifying action, the decrease in the number of sand beaches has influenced the quality of seawater. The excess discharge of wastes into the environment has impacted the coastal marine environment. First of all, nutrients discharged through anthropologic activities have caused eutrophication. Accumulated nutrients in enclosed and semienclosed water areas have led to the formation of red and blue tides which have killed fish. Hazardous materials have also been discharged into the environment. They have been transported in the form of solutes, adsorbents, or solids (precipitates) into water areas, such as rivers, lakes, ponds, and seas. These substances are potentially taken up by the organisms at the starting point of the coastal marine environment. Subsequently most sea animals become contaminated through the bioaccumulation within the food chain (Bright et al., 1995; de Mora et al., 2004; Hayter, 2006; McLachlan et al., 2001). In this section, rehabilitation techniques for sediments are introduced.

In Situ Remediation and Management of Contaminated Sediments

145

6.3.1 Eutrophication Eutrophication has been considered to be a phenomenon due to water conditions only. However, it was found that the quality of sediments strongly influences the eutrophication of surface water. This is because sediments contain nutrients which can be released into the overlying water. In general, nutrients can be released when the organic matter in sediments is degraded. The biodegradation of organic matter causes the decrease in dissolved oxygen (DO), because microorganisms consume DO during their activity under aerobic conditions. The decrease in DO leads to anaerobic conditions, and incomplete degradation takes place. As a result, the production of sulfides, such as hydrogen sulfide, occurs. Aeration can be a measure to increase DO, but it may stimulate bacteria to degrade organic matter under aerobic conditions. As a result, nutrients will be released into the water again, and eutrophication will continue to occur. Since it is evident that the organic-rich sediment is problematic, it is better to remove some amount of organic matter with nutrients from the water area. This can be achieved by resuspending the sediment particles and filtering them. The idea and experimental results are introduced in a later section. Another way to control eutrophication may be by sand capping the sediment. However, the reduction of the release of nutrients from the sediment may be only for a short time, because of the time lag for advection and diffusion of nutrients from the sediment. Some data show that the release of nutrients increases after a lag period. In addition, organic matter will biodegrade under anaerobic conditions. This can then lead to the production of gases such as methane, carbon dioxide, and hydrogen sulfide. These gases can accumulate and then diffuse or be transported by advection through the cap material. This can facilitate transport of contaminants though contaminant solubilization or by providing channels through the cap. As long-term measures include capping methods, materials other than sand can be used as described later.

6.3.2 Contamination As described earlier in the book, many types of toxic and hazardous substances have been discharged into the environment. The substances have accumulated into the sediments and can be released into water as well as nutrients. The toxic and hazardous substances are adsorbed, retained, or precipitated. Metals are adsorbed onto the inorganic or organic particles, or precipitated as hydroxides or oxides. Aluminum and magnesium are constituents of mineral particles. Polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs) are also retained in the sediments, in addition to TBT and triphenyl tin (TPT). In general, these substances are concentrated more in the smaller particles and organic matter. The measures for remediation of sediments can be similar to those used for nutrient problems (i.e., removal of organic matter by resuspension, capping, or dredging).

146


6.3.3 Distribution of Contaminated Particles Smaller particles have a higher specific surface area than coarse particles. Therefore, the concentrations of retained substances on sediments are influenced by the particle size, as shown in Figure 6.5 and Figure 6.6. The horizontal axis in these figures is taken as content finer than 0.075 mm instead of the particle size. Fukue et al. (2006) showed that particles of grain size diameter at which 10% dry weight are finer ( RDX > HMX (octahydro-1,3,5,7-tetranitro1,3,5,7-tetrazocine) were found. Shewanella and Halomonas bacterial isolates were found (Zhao and Hawari, 2008). Khodadoust et al. (2009) showed that PCBs could be degraded anaerobically with the addition of iron periodically. The biodegradation of PCBs in lake and marine sediments was monitored for nine months, and the addition of ion in dosages between 0.01 and 0.1 g/g enhanced degradation.

7.5.1 Slurry Reactors Slurry bioreactors use 5% to 20% solid content in a highly agitated treatment. Mass transfer, aeration, and environmental conditions can be optimized more easily than for in situ remediation. This type of treatment is particularly applicable for compounds of low biodegradability such as PCBs and PAHs. Slurry methods can be used because dewatering is not required (Figure 7.16). There are also other limitations as discussed for sediment washing. Bioremediation is a low-cost technology and therefore has the potential for wide use. However, metal remediation technologies are not as developed as organic treatments. Costs are in the range of $15 to $200 US per tonne (Environment Canada, 1995). Surfactants can be added to enhance contaminant solubility, or the natural bacteria could be stimulated to produce natural biosurfactants. The latter approach was investigated for an oil and heavy metal-contaminated harbor soil (Jalali and Mulligan, 2008). It has shown potential and could be applied to contaminated sediments. Some preliminary results showed that, by the end of the 50-day experiment, nutrient amendments led to the enhancement of biosurfactant production up to three times their critical micelle concentration (CMC). Further experiments were performed to investigate the production of biosurfactants by limiting the inorganic source of nitrogen. Results showed an enhancement of biosurfactant production by 40%. The produced biosurfactants were also able to solubilize 10% of TPH and 6% of the metal content of the soil. These biosurfactants were produced by the indigenous soil microorganisms using organic contaminants as the sole carbon source. Furthermore, the produced biosurfactants showed potential to enhance biodegradation of petroleum hydrocarbons as well as to improve flushing of the remaining soil pollutants from the soil. Baciocchi and Chiavola (2009) evaluated the use of a sequential batch reactor for treating sediment in a slurry phase. Degradation rates of PAHs of 90% to 95% could be achieved after optimization. Based on a 10% sediment concentration and laboratory tests, it was estimated that 4.8 kg/m3/day could be treated.

7.5.2 Landfarming Landfarming includes mixing the surface layer of soil with the contaminated sediment (Rittmann and McCarty, 2001) (Figure 7.17). Soil microorganisms are utilized for biodegradation of the contaminants. The resulting product is compost.

192

Sediments Contamination and Sustainable Remediation Contaminated sediment

Screen

Oversize material

Recycle water

Clean water Thickener or Plate frame press

Nutrients and microbes

Air

Cleaned sediment for disposal or reuse

Figure 7.16 Slurry reactors for bioremediation of sediments.

Moisture must be monitored, and nutrients can be added to enhance biodegradation. Occasional turning of the soil increases the oxygen content and permeability of the sediment/surface soil mixture. The process is simple, but could lead to contaminant volatilization and leaching. Therefore, monitoring is required. Land requirements can be extensive. In the United States and Belgium, bioremediated dredged materials has been mixed with compost and/or municipal sewage sludge to produce soil for landscaping projects, and in Germany it has been used in orchards. Berm Contaminated sediment Groundwater monitoring well

Liner

Tiller

Nutrient solution

Pump

Sand cushion

Aquifer

Figure 7.17 Landfarming process for bioremediation of sediments.

Dredging and the Remediation of Dredged Contaminated Sediments Clay/Organic matter agglomerate

Bacterial cells

193

Hydrated Daramend particles colonized by native soil bacteria

Mineral particle

Hydrocarbons desorb from soil and diffuse to Daramend particle surface where biodegradation occurs Clay platelets

Fungal mycelia Water film

Organic matter sesquioxides

Figure 7.18 Schematic of the DARAMEND technology (from Mulligan, 2002).

An additive that has been used with landfarming is DARAMEND™. It is a solidphase amendment (Figure 7.18) to promote anoxic conditions to enhance the bioremediation of pesticides such as toxaphene, DDT, DDD, and DDE. The reduction in the redox potential enhances the dechlorination of organochlorine compounds. With tilling equipment, the material can be mixed in to a depth of 2 ft. Hydrated lime is used to maintain the pH between 6.6 and 8.5. Redox potential and moisture were monitored and evaluated at a Superfund Site (Montgomery, AL) of a soil/sediment contaminated with pesticides (USEPA, 2004). Approximately 4500 tons were treated, and all contaminants reached specified levels. Santiago et al. (2003) evaluated DARAMEND for PAH-contaminated sediment. However, PAH concentrations were higher than expected (average of 900 ppm) and thus could not be reduced by bioremediation to CCME criteria (260 ppm) in bench-scale experiments. Thermal treatment was successful, however. Metal removal can be accomplished in conjunction with organic removal. For example, Vega has developed a landfarming process that uses chelating organic acids with nutrients and soil conditioners to initiate biodegradation. The organic acids can chelate metals, as well as promote organic degradation. Temperature, moisture content, and pH need to be controlled as in any microbial process. It has mainly been applied for petroleum contamination. Retention times can be long (30 to 120 days).

7.5.3 Composting Composting involves the biodegradation of organic materials to produce carbon dioxide and water. Typical temperatures are in the range of 55 to 65°C due to the heat from the biodegradation process. Animal or vegetable wastes such as sewage

194


sludge are often used as organic amendments. Bulking agents such as wood chips are added to increase the porosity of the material. Moisture content and temperature must be monitored. Composting processes include windrows and biopiles and invessel composting. Composting of a contaminated sediment was evaluated by Khan and Anjaneyulu (2006). A ratio of 10 kg of sediment with 0.5% fertilizer and 50% compost was used. The contaminants present in the sediment included phenols (16 to 24 mg/kg) and benzene (3.4 mg/kg). Fertilizer was added to increase the nutrient content, and compost was used as the inoculum of microorganisms. Wood chips were added as a support and aerating material in the pile for composting. The parameters, pH, total volatile solids, microbial count, temperature, and contaminant concentration, were monitored over the period of five weeks. Approximately 80% to 85% of the phenols were degraded, whereas benzene was almost completely biodegraded. Therefore, composting was shown to be technically feasible at lab scale. Myers and Williford (2000) examined the bioremediation of contaminated sediments in a confined disposal facility (CDF). Composting (windrows and biopiles), landfarming, and land treatment were examined (Table 7.1). The contaminants included PAHs, PCBs, and PCDDs/Fs (dioxins). Land treatment is similar to land farming, except that the contaminated sediments are tiled and interact with the surrounding soil. Monitoring is essential due to potential leaching and volatilization of contaminants. Laboratory studies have shown the biodegradability of these compounds, but there is a lack of information on the treatment of dredged material. Composting and land treatment have potential to be cost effective, but require understanding of the biological processes and the technology. Pilot and demonstration studies are needed to do this. Subsequent composting tests were not successful in remediating PAHs. PCB degradation may be a little more promising. The factors and conditions were not well understood, and further research work is needed (Myers et al., 2003). Table 7.1 Comparison of Bioremediation Technologies Parameter

Windrow Composting

Applicability

Explosives, PAHs

Site requirements

Excavation and special mixing equipment Bulking agents increase volume and may need to be removed $248/m3

Limitations

Cost

Source: Adapted from Myers and Williford, 2000.

Landfarming

Biopile Composting

Diesel fuel, fuel oil, PCBs, pesticides Excavation and earthmoving equipment Permanent structures required

Fuels, solvents

Less than $98/m3

$35 to 130/m3

Excavation and earthmoving equipment Static process without mixing

Dredging and the Remediation of Dredged Contaminated Sediments

195

7.5.4 Bioleaching Bioleaching involves Thiobacillus sp. bacteria which can reduce sulfur compounds under aerobic and acidic conditions (pH 4) at temperatures between 15 and 55°C, depending on the strain. Leaching can be performed by indirect means, acidification of sulfur compounds to produce sulfuric acid which then can desorb the metals on the soil by substitution of protons. Direct leaching solubilizes metal sulfides by oxidation to metal sulfates. In laboratory tests, Thiobacilli were able to remove 70% to 75% of heavy metals (with the exception of lead and arsenic) from contaminated sediments (Karavaiko et al., 1988). Options are available for bioleaching, including heap leaching and bioslurry reactors. Sediments require lower pH values to extract the metals because they have already been exposed to oxidizing conditions. For both heap leaching and reactors, bacteria and sulfur compounds are added. In the reactor, mixing is used, and pH can be controlled more easily; leachate is recycled during heap leaching. Copper, zinc, uranium, and gold have been removed by Thiobacillus sp. in biohydrometallurgical processes (Karavaiko et al., 1988). Percolation field tests were run by Seidel et al. (1998). They found that addition of sulfur as a substrate provided better leaching results than sulfuric acid. Approximately 62% of the metals were removed by percolation leaching after 120 days for the oxic sediments. Only 9% of the metals were removed from the anoxic sediments. They indicated that anoxic sediments are less suitable for treatment and must be ripened as a pretreatment.

7.5.5 Bioconversion Processes Microorganisms are also known to oxidize and reduce metal contaminants. Mercury and cadmium can be oxidized, while arsenic and iron can be reduced by microorganisms. This processs (called mercrobes) has been developed and tested in Germany at concentrations greater than 100 ppm. Since the mobility is influenced by its oxidation state, these reactions can affect the contaminant mobility. Chromium conversion is also affected by the presence of biosurfactants. A study was conducted by Massara et al. (2007) on the removal of Cr(III) to eliminate the hazard imposed by its presence of kaolinite. The effect of addition of negatively charged biosurfactants (rhamnolipids) on chromium-contaminated soil was studied. Results showed that the rhamnolipids have the capability of extracting a portion of the stable form of chromium, Cr(III), from the soil. The removal of hexavalent chromium was also enhanced using a solution of rhamnolipids. Results from the sequential extraction procedure showed that rhamnolipids remove Cr(III) mainly from the carbonate and oxide/hydroxide portions of the soil. The rhamnolipids also have the capability of reducing close to 100% of the extracted Cr(VI) to Cr(III) over a period of 24 days.

7.5.6 Phytoremediation Some plants have been shown to retain metals in their roots, stems, and leaves (Hazardous Waste Consultant, 1996). Vegetative caps consisting of grasses, trees,

196


and shrubs can be established in shallow fresh water. The resulting vegetative mat can hold sediments in place. The construction of wetlands is growing for wastewater treatment, and thus the knowledge on wetland configurations is growing. However, vegetative caps have not yet been applied to the remediation of sediments (Mulligan et al., 1999). It is more likely that this technology will be used as an in situ method of reducing large volumes of sediment transport. However, phytoremediation could be implemented where dredged sediments have been placed in contained areas and a wetland is then constructed to remediate and contain the sediments. Lee and Price (2003) indicated that, although phytoextraction of Pb with chelates may be troublesome due to potential leaching into groundwater, immobilization and phytostabilization can be appropriate in CDFs. The site could potentially be restored for beneficial use as a wildlife habitat.

7.6 Beneficial Use of Sediments There are two choices regarding the handling of dredged materials: beneficial use or disposal. For the use of dredged materials, it is problematic that dredged materials are too soft and contaminated. In addition, the volume of dredged materials is often very large. Since there is a lack of disposal sites, beneficial use of the contaminated dredged sediments is promoted. Between the alternatives, there may be various choices, as shown in Figure 7.19. Beneficial use of dredged sediments has been investigated by many researchers (Sadat Associates Inc., 2001; Colin, 2003; Comoss et al., 2002; Dermatas et al., 2002; Douglas et al., 2005; Dubois, 2006; Maher, 2005; Maher et al., 2004, 2006; Siham et al., 2008; Yozzoa and Robert, 2004; Zentar et al., 2008). Decontamination Disposal

Treatment

Beneficial use

Contaminated Beneficial use

Disposal

Separation

Beneficial use

Disposal Contaminated

Non-contaminated Dredged materials

Figure 7.19 Reuse strategies for decontaminated sediments.


197

Many studies have been reported from the Great Lakes project (Great Lakes Commission, 2004). It is necessary to improve the materials for use as construction materials. Zentar et al. (2008) investigated the mechanical behavior and environmental impacts of a test road built with marine dredged sediments. They improved the mechanical properties of fine dredged materials by adding dredged sand. Basically, the result can be dependent on the grain size distribution of the mixture (Fukue et al., 1986). The leaching test results showed no significant leachate production from the materials, because of the initially low concentration of toxic substances for the raw materials and high pH values used. In fact, sediments have been in water, and the amount of leachate during leaching tests is usually low (Fukue et al., 2001). It is suggested that leaching tests should be performed for various pH values, especially for lower pH values. Contaminated dredged material is a problem worldwide. For this reason, the disposal of dredged materials into the ocean is prohibited (London Convention). Jones et al. (2001) compared various decontamination techniques used for the dredged sediments from the port of New York/New Jersey. In the report, a total of nine different technologies were introduced. Experiments were performed at bench scale (15 liters). The approaches included sediment washing, solvent extraction, thermal desorption, and thermal destruction. These technologies can be viewed as components of a treatment train for dredging, treatment, and beneficial use of contaminated dredged material. They also discussed beneficial use and commercialization of the products. The sediment washing can lead to manufactured soils or material from residential landscaping (USEPA, 2005). The thermal treatment can produce manufactured grade cement comparable to Portland cement. The treatment train included dewatering, pelletization (a type of solidification by addition of shale fines and extrusion), and transportation to an aggregate facility. After pelletization, the pellets are treated in a rotary kiln, exploding the organic matter. The final product can be used for various geotechnical applications including concrete production and insulation of pipelines. The last process, vitrification, produced a glassy material that could be used for architectural tiles. Beneficial use is not normally considered in treatment processes. However, it should be to enhance the sustainability of the process. Cost-effectiveness is a major consideration, and contaminant release must not occur. Besides those already discussed, alternative products can include: • • • • • • •

Construction fill Municipal landfill cover Restoration of mined areas Capping material Building materials Enhancing beach areas with clean sand Habitat restoration in dredged areas or wetlands

Artificial sand beaches and tidal flats are created for one of the following purposes:

198


1. Formation of clean beach for resort areas and parks 2. Farming for shellfish 3. Recovery of beach following reclamation 4. Rehabilitation of coastal marine environment

Sand beaches and tidal flats possess natural capabilities for cleaning seawater under repeating waves and tides. This capability arises from a combination of their ability to filter a large amount of suspended solids (mostly organic matter) and the dissolution of the suspended solids by microorganisms. Although the organic matter entrapped in the sand pores is food for microorganisms and benthic animals, there are no easy means to quantify the process and its benefits. Evaluation of the impacts arising from construction of the tidal flats and beaches cannot be readily performed. In part, this is due to the dynamic processes initiated by the actions of currents and waves. Stabilization of the new beaches and tidal flats will be a long-term process. The use of breakwaters on beaches brings with it problems of decrease in redox in the region due to the dead organisms and excrements. One of the three tidelands is Kansai Rinkai Park, with an area of 270,837 m2, which was created artificially by the Tokyo Metropolitan Government in 1965, at a time when Tokyo Bay was losing its valuable natural environment. The area incorporates vast tidelands, which were once the breeding areas for birds and were also once abundant with fish and shellfish. Geotextile tubes can be used to protect coastline from waves and tides—as has been utilized in some countries. The tubes, which can be installed along the coastline, are a few meters in diameter and a few kilometers in length and can be filled with dredged sediment. They can also serve as a breakwater for man-made islands and wetlands.

7.7 Confined Disposal In the case that sediment is contaminated, in situ/ex situ remediation can be performed. If remediation is not possible, the dredged materials can be disposed of in a proper manner. Containment of dredged material is carried out in confined disposal facilities in dikes near the shore, island, or on the land facilities. The facilities must be designed for dredging purposes and to contain the contaminants. Landfills have been used widely for disposal of dredged materials. The sediments must be previously dewatered such as in a contained disposal facility because landfill facilities cannot handle slurries. Large volumes cannot usually be accommodated because landfills do not have the capacity. Potential mechanisms for contaminant release are due to leachates, runoff, effluents, volatilization, uptake by plants, and ingestion by animals. Therefore, pretreatment by stabilization/solidification may be necessary. Oxygenation of sediments by the rain can lead to metal contamination of the groundwater. The cost is in the range of $20 to $65 per cubic meter (USEPA, 1993). Containment facilities can be used for storage, dewatering, and pretreatment for other processes. These costs are usually less than those for landfill. Areas for contained aquatic disposal, the placement of material in a confined aquatic area called a confined disposal facility (CDF), can be strategically placed in depressions and confined by dikes. This technique can be used for disposal of contaminated sediments.


199

Clean material can be placed above and at the edges. The USACE and USEPA (2003) have reviewed the use of CDFs for dredging projects in the Great Lakes. Confined aquatic disposal (CAD) is used for placement of dredged material in a natural or excavated depression. It has been used mainly for navigational purposes such as in Boston Harbor, not disposal of contaminated material. It may be appropriate if landfill disposal or in situ capping is not possible. Maintenance costs are low, and there can be an increased resistance to erosion. Depths can be a few to more than 10 m, and widths are in the range of 500 to 1500 m. As they are filled, capping is used. Another approach is to place the material in woven or nonwoven permeable synthetic fabric bags, geotextile tubing, or containers (NRC, 1997). Costs at the demonstration in California were approximately $65 per m3 (Clausner, 1996). The contaminants must not seep through the fabric into the water, and these uncertainties must be further investigated. The U.S. Corps of Engineers have used geocontainers to store dredged sediments. The geocontainers are made of geosynthetic material and assembled by a seaming technique. Large quantities of dredged material are contained in the geocontainers after filling by hydraulic or mechanical filling equipment. This can be done in situ or in split-hull barges. If the latter is used, the sediments can be pumped as a slurry into the bags. This is followed by stitching of the bags and allowing them to fall through the split of the barge. The geocontainers dropped from barges into open water can form underwater berms, dikes, or other structures. They are designed to resist degradation under environmental conditions. The containers can be used (Rankilor, 1994) as breakwaters, near beaches or offshore, to stabilize sand dunes or wetlands or for dike construction. In the Mississippi River near Baton Rouge, the Red Eye Crossing Soft Dikes Demonstration Project (Hall, 1998) used polypropylene bags filled with coarse river sand as soft dikes. Millions of dollars can be saved because less dredging is required. The soft dikes are placed lower than the nearby sandbar where the bags are filled. Both small geobags of three cubic meters and large geocontainers of 200 to 300 cubic meters are used. The project has gone well for over four years. In Japan, dredged sediments are basically regarded as waste materials. Therefore, the dumping of dredged materials into the ocean is basically prohibited, and dredging cannot be achieved unless the site for disposal is ready. This is mainly because sediments are usually organic rich and more or less contaminated. There is one exception when dredging of sediments will be recommended. Because there is a guideline for dioxin-contaminated sediments, when the contamination of sediments with dioxin is found, dredging is one of the effective methods to solve the problem. The selective disposal flow sheet for dioxin-contaminated sediments is shown in Figure 7.20 (Japanese guideline for investigation, treatment and measure for dioxin contamination of sediments, Revised version, 2008). The fractions of contaminated dredged materials or highly concentrated dredged materials with toxic substances, which cannot be beneficially used, have to be disposed of without subsequent contamination.

200

Sediments Contamination and Sustainable Remediation Selective Final Disposal Yes

No

>150pg-TEQ/g, 10pg-TEQ/L

Conc.?

Reclamation or Landfill Lower than or equal to 150g-TEQ/g and 10pg-TEQ/L

Landfill

Lower than or equal to 150g-TEQ/g

Construction Materials Reclamation with the guideline provided by PPD 5.1.1 Reclamation with the guideline provided by PPD 5.2. In the case of 3000pg-TEQ/g, controlled disposal for high risk materials is required and degradation of dioxin should be promoted.

Conc.?

>1000pg-TEQ/g

Reclamation

Degradation

Lower than or equal to 1000pg-TEQ/g

Degradation

To avoid diffusion of dioxin, controlled disposal or landfill with facilities is required In the case of 3000pg-TEQ/g, controlled disposal for high risk materials is required.

Figure 7.20 Selective flow chart of dioxin-contaminated sediment.

7.8 Comparison between Treatment Technologies A major problem in comparing treatment technologies is that very few studies use the same sediment. Recently, however, the EPA’s Great Lakes National Programs Office performed a study on Trenton Channel sediments (Cieniawski, 1998). Five technologies including solid phase extraction, solidification (Growth Resources), soil washing (Biogenesis), thermal desorption (Cement Lock), and plasma vitrification (Westinghouse) were evaluated. A drum of 208 L of sediments was given to each company. The sediments contained PAHs, mercury, lead, PCBs, and oil and grease. Solid-phase extraction had no significant effect on total metals. High-temperature plasma vitrification was effective for greater than 90% of the contaminants including the metals. Conversion of the sediment into the form of glass will allow its use as an aggregate or glass tile or in glass fiber products. Cement Lock was very effective for all contaminants with the exception of metals (20% and 90% reduction). Heavy metals are locked in the cement matrix, while volatile metals, such as mercury and arsenic are volatilized. Volume reduction is a major advantage of the process. In addition the cement end product can be used in construction, eliminating disposal costs. Although soil washing was very effective for leachable metals, it was only partially effective for total metals. Wastes were reduced to reusable oil, treated water, and soil for backfill. Overall, most of the technologies were able to remove mercury but not lead to residential criteria. Only industrial and commercial criteria could be achieved for lead. Estimation of the costs for the technologies showed that the


201

highest capital costs were $10 to $15 million for the vitrification process and $20 million for Cement Lock, while those for soil washing were $3.5 million, and for solidification $0.7 million (Snell Environmental Group, 1997). Operating costs were the highest for soil washing ($118/m3), followed by vitrification ($110/m3). The lowest operating costs were for the thermal desorption ($63/m3) and solidification ($59/ m3). Although these tests were performed at bench scale, they are useful in the comparison of technologies because they are on the same basis. Because Cement Lock and vitrification achieved the highest removal efficiencies and produced useful final products, they were recommended for further pilot tests. In 1999, it was decided to remove 23,000 m3 of contaminated sediment from Black Lagoon and treat a fraction with Cement Lock (Zarull et al., 1999).

7.9 Case Studies of Remediation 7.9.1 Remediation of Sediments Contaminated with Dioxin In Japan, dioxin is designated as a special substance to be extremely toxic for humans, and the guideline provides that sediments are contaminated if the dioxin level is higher than 150 pg-TEQ/g. It was found that the sediments in Tagono-ura port in Fuji City, Japan were contaminated with dioxin (Table 7.2). Based on the regulations concerning sediments contaminated with dioxin, the sediments had to be remediated. The investigation prior to the project showed the contamination level and volume as follows. The contaminated area was 349,000 m2. The project was led by the committee established in the Shizuoka Prefecture. The committee examined three techniques (i.e., dredging, capping, and in situ solidification) and selected dredging and disposal. The committee selected dredging using the grab technique, because of low contamination in the surrounding area. During the dredging, a silt fence was used to avoid diffusion of contaminated particles. The basic process from dredging to final disposal is shown in Figure 7.21. The treatment consisted of solidification, separation, and dewatering. Solidification prevents contamination from spreading and dioxin from leaching. Separation and dewatering was used to reduce the volume. Monitoring was made to inspect the contamination from the resuspended particles. Since measuring dioxin is expensive, the committee chose the following procedure. Table 7.2 Contamination Levels and Volume of Sediments in Tagono-ura, Japan Concentration (pg-TEQ/g) 150–1000 1000–3000 More than 3000

Contaminated Volume (m3) 471 000 70 000 1000

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Transport

Disposal

Detoxification Transfer to the Land

Treatment No release

Solidification

Reduction of volume Dredging

Separation and dewatering

Shipping

No leaching

Solidification

Figure 7.21 Basic process from dredging to disposal.

The relationships between the concentration of dioxin and turbidity in seawater were determined with different site locations. The relationships were linear, and correlation factors were very high. For example, the following relationship was determined. Quality of seawater with dioxin CD (pg-TEQ/L)

= 0.1533 Tb

(R2 = 0.9986)

where CD is the concentration of dioxin in seawater, and Tb is the turbidity (NTU). This shows that dioxin is adsorbed to the suspended solids. Using the relationship, CD values were estimated from the measured turbidity. In fact, the relationships obtained were different for the different site locations. The relationships were expressed by:

C D = kTb

where k is a proportional constant. The allowable level was decided as 1 pg-TEQ/L. Therefore, the following guideline was used for the control of seawater quality.

Tb
20 samples and >75% correct classification as toxic). PEL: probable effect level, dry weight (Smith et al., 1996) SEL: severe effect level, dry weight (Persaud et al., 1993) TET: Toxic effect threshold, dry weight (EC & MENVIQ, 1992) ERM: Effects range median; dry weight (Long and Morgan, 1991) PEL-HA28: probable effect level for Hyalella azteca; 28-day test; dry weight (USEPA, 1996) NG: No guideline

Appendix C: Prediction of Sediment Toxicity

275

References Environment Canada and Ministere de l’Environnement du Quebec (EC and MENVIQ). 1992. Interim criteria for quality assessment of St. Lawrence River sediment. ISBN 0-66219849-2, Environment Canada, Ottawa, ON. Long, E.R. and Morgan, L.G. 1991. The potential for biological effects of sediment sorbed contaminants in the National Status and Trends Program. NOAA Technical Memorandum NOS OMA 52. National Oceanic and Atmospheric Administration, Seattle, WA, 175 pp. + Appendices. MacDonald, D.D., Ingersoll, C.G., and Berger, T. 2000. Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Arch. Environ. Contam. Toxicol. 39: 20–31. Persaud, D., Jaagumagi, R., and Hayton, A. 1993. Guidelines for the protection and management of aquatic sediment quality in Ontario. Water Resources Branch, Ontario Ministry of the Environment, Toronto, ON, 27 pp. Smith, S.L., Macdonald, D.D., Keenelysied, K.A., Ingersoll, C.G., and Field, J. 1996. A preliminary evaluation of sediment quality assessment values for freshwater ecosystems. J. Great Lakes Res. 22: 624–638. USEPA. 1996. Calculation and evaluation of sediment effect concentrations for the amphipod Hyalella azteca and the midge Chironomus riparius. EPA 905/R-96/008, Chicago, IL.

Appendix D: International Sediment Quality Criteria

277

278


Hong Kong Hong Kong classifies sediments based on their contaminant levels with reference to the Chemical Exceedance Levels (CEL) shown below (Hong Kong Environment and Transport Bureau (ETWB 34/2002), http://www.devb-wb.gov.hk/UtilManager/ tc/2002/C-2002-34-0-1.pdf). Sediment Quality Criteria for the Classification of Sediments in Hong Kong Lower Chemical Exceedance Level (LCEL)

Contaminants

Cadmium (Cd) Chromium (Cr) Copper (Cu) Mercury (Hg) Nickel (Ni)* Lead (Pb) Silver (Ag) Zinc (Zn)

Arsenic (As)

Upper Chemical Exceedance Level (UCEL)

Metals (mg/kg dry wt.) 1.5 80 65 0.5 40 75 1 200

4 160 110 1 40 110 2 270

Metalloid (mg/kg dry wt.) 12

42

Organic-PAHs (µg/kg dry wt.) 550 1700

3160 9600

Total PCBs

Organic-non-PAHs (µg/kg dry wt.) 23

180

Tributyltin*

Organometallics (µg TBT/L in Interstitial water) 0.15

Low Molecular Weight PAHs High Molecular Weight PAHs

0.15

*The contaminant level is considered to have exceeded the UCEL if it is greater than the value shown. The sediment is classified into three categories based on its contaminant levels: Category L: sediment with all contaminant levels not exceeding the Lower Chemical Exceedance Level (LCEL). The material must be dredged, transported, and disposed of in a manner which minimizes the loss of contaminants either into solution or by resuspension. Category M: sediment with any one or more contaminant levels Lower Chemical Exceedance Level (LCEL) and none exceeding Upper Chemical Exceedance Level (UCEL). The material must be dredged and transported with care and must be effectively isolated from the environment upon final disposal unless appropriate biological tests demonstrate that the material will not adversely affect the marine environment. Category H: Sediment with any one or more contaminant levels exceeding Upper Chemical Exceedance Level (UCEL). The material must be dredged and transported with great care and must be effectively isolated from the environment upon final disposal.

279


The Republic of Korea Action List for the Degraded Material Disposal at Sea in the Republic of Korea Parameter Chromium and its compounds Zinc and its compounds Copper and its compounds Cadmium and its compounds Mercury and its compounds Arsenic and its compounds Lead and its compounds Nickel and its compounds Total polychlorinated biphenyls Total polyaromatic hydrocarbons

1st Level (Upper Level) mg/kg Dry Weight 370 410 270 10 1.2 70 220 52 0.180 45

2nd Level (Lower Level) mg/kg Dry Weight 80 200 65 2.5 0.3 20 50 35 0.023 4

Notes: Total polychlorinated biphenyls is the sum of contents of PCB-28, PCB-101, PCB-138, PCB-153, and PCB-180 congeners in a sample. Total polyaromatic hydrocarbons is sum content of naphthalene, phenathrene, anthracene, benzo(a)pyrene, benzo(a) anthracene, fluoranthene, benzo(b), and fluoranthene in a sample.

Australia and New Zealand Australia and New Zealand Guidelines for Fresh and Marine Water Quality National Ocean Disposal Guidelines for Dredged Material Environment Australia, May 2002, ISBN 0 6425 4831 5. http://www.environment.gov.au/ coasts/pollution/dumping/guidelines/pubs/guidelines.pdf.

Canada Canadian Council of the Environment. 2001. Canadian sediment Quality Guidelines for the protection of aquatic life. Updated. Environmental quality guidelines, 1999. Canadian Council of Ministers of the Environment, Winnipeg, Canada. CCME. 1999. Protocol for the Derivation of Canadian Sediment Quality Guidelines for the Protection of Aquatic Life, CCME EPC98E. http://www.ccme.ca/assets/pdf/sedqg_protocol.pdf. Canadian Disposal at Sea Program website. http://www.ec.gc.ca/seadisposal/reports/index_e. htm#sqg.

United States USEPA National Sediment Inventory. 2004. Appendix C—Screening Values for Chemicals Evaluated, http://www.epa.gov/waterscience/cs/report/2004/nsqs2ed-complete.pdf#page=213.

280


NOAA. 1999. Sediment Quality Guidelines developed for the National Status and Trends Program, National Oceanic and Atmospheric Administration, http://response.restoration.noaa.gov/book_shelf/121_sedi_qual_guide.pdf. USEPA. 1997. Ecological Risk Assessment Guidance for Superfund: Process for Designing and Conducting Ecological Risk Assessments. EPA 540-R-97-006, 1997. U.S. Environmental Protection Agency, Office of Solid Waste and Emergency Response, Washington, DC, http://www.epa.gov/oswer/riskassessment/ecorisk/ecorisk.htm.

USACE USEPA/USACE. 1991. Evaluation of Dredged Material Proposed for Ocean Disposal. Testing Manual, EPA 503/8-91/001. U.S. Environmental Protection Agency and U.S. Army Corps of Engineers, Washington, DC. USEPA/USACE. 1998. Evaluation of dredged material proposed for discharge in waters of the U.S. testing manual. EPA-823-B-98-004, Washington, DC, http://el.erdc.usace.army. mil/elmodels/pdf/inlandb.pdf. USGS. 2002. Prediction of Sediment Toxicity using consensus based freshwater sediment quality guidelines. EPA/905/R-00/007, June 2000, United States Geological Survey (USGS), http://www.cerc.usgs.gov/pubs/center/pdfdocs/91126.pdf.

U.S. State Guidelines Florida 1994 Florida Sediment Quality Assessment Guidelines (SQAGs)

Chemical Parameter Arsenic Cadmium Chromium Copper Lead Mercury Silver Zinc Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene

Sediment Quality Assessment Guidelines TEL

Sediment Quality Assessment Guidelines PEL

mg/kg Dry Weight (Parts per Million (ppm) Dry)


7.24 0.676 52.3 18.7 30.2 0.13 0.733 124 µg/kg 34.6 5.87 6.71 21.2 86.7 46.9

41.6 4.21 160 108 112 0.696 1.77 271 µg/kg 391 128 88.9 144 544 245

281


1994 Florida Sediment Quality Assessment Guidelines (SQAGs)

Chemical Parameter 2-Methylnaphthalene Total lmw-PAHs Fluoranthene Pyrene Benz(a)anthracene Chrysene Benzo(a)pyrene Indeno(1,2,3,-c,d)pyrene Dibenzo(a,h)anthracene Pesticides Chlordane p,p′-DDD p,p′DDE p,p′-DDT Total DDT Dieldrin Lindane Bis(2-ethylhexyl)phthalate Total PCBs

Sediment Quality Assessment Guidelines TEL

Sediment Quality Assessment Guidelines PEL



20.2 312 113 1,000 74.8 108 88.8 34 113 2.26 1.22 2.07 1.19 3.89 0.715 0.32 182 21.6

201 1442 1494 1400 693 846 763 88 1494 4.79 7.81 374 4.77 51.7 4.3 0.99 2647 189

Source: http://www.dep.state.fl.us/waste/quick_topics/publications/pages/default.htm. Note: TEL= toxic effect level; PEL= probable effect level.

New York New York State Department of Environmental Conservation, Division of Fish, Wildlife and Marine Resources. 1999. Technical Guidance for Screening Contaminated Sediments, Jan. 1999, http://www.dec.ny.gov/docs/wildlife_pdf/seddoc.pdf.

Washington State Sediment Quality Chemical Criteria The Sediment Management Standards currently contain two sets of numeric chemical criteria that apply to Puget Sound marine sediments:

282


1. The “no effects” level—the Sediment Quality Standards, WAC 172-204320—used as a sediment quality goal for Washington State sediments (shown below), and 2. The “minor adverse effects” level—The Sediment Impact Zone Maximum Level, WAC 173-204-420; and the Sediment Cleanup Screening Level/ Minimum Cleanup Level, WAC 173-204-520—used as an upper regulatory level for source control and cleanup decision making (shown below).

To understand the context in which the criteria are used, see the Sediment Management Standards regulation.

Chemical Parameter Arsenic Cadmium Chromium Copper Lead Mercury Silver Zinc LPAH (b,d) Naphthalene Acenaphthylene Acenaphthene Fluorene Phenanthrene Anthracene 2-Methylnaphthalene HPAH (b,e) Fluoranthene Pyrene Benz(a)anthracene Chrysene Total Benzofluoranthenes (b,f) Benzo(a)pyrene

Sediment Quality Standards WAC 173-204-320 (a)

Sediment Impact Zone Maximum Level, WAC 173-204-420 (a); and Sediment Cleanup Screening Level/Minimum Cleanup Level, WAC 173-204-520 (a)


mg/kg Dry Weight (Parts Per Million (ppm) Dry)

57 5.1 260 390 450 0.41 6.1 410 mg/kg Organic Carbon (C) (ppm Carbon) 370 99 66 16 23 100 220 38 960 160 1,000 110 110 230 99

93 6.7 270 390 530 0.59 6.1 960 mg/kg Organic Carbon (C) (ppm Carbon) 780 170 66 57 79 480 1200 64 5300 1200 1400 270 460 450 210

Appendix D: International Sediment Quality Criteria Indeno(1,2,3,-c,d)pyrene Dibenzo(a,h)anthracene BENZO(G,H,I)PERYLENE 1,2-Dichlorobenzene 1,4-Dichlorobenzene 1,2,4-Trichlorobenzene Hexachlorobenzene Dimethyl Phthalate Diethyl Phthalate Di-n-butyl Phthalate Butyl Benzyl Phthalate Bis(2-ethylhexyl) Phthalate Di-n-octyl Phthalate Dibenzofuran Hexachlorobutadiene n-Nitrosodiphenylamine Total PCBs (b) Phenol 2-Methylphenol 4-Methylphenol 2,4-Dimethyl Phenol Pentachlorophenol Benzyl Alcohol Benzoic Acid

34 12 31 2.3 3.1 0.81 0.38 53 61 220 4.9 47 58 15 3.9 11 12 µg/kg Dry Weight (Parts per Billion (ppb) Dry) 420 63 670 29 360 57 650

283 88 33 78 2.3 9 1.8 2.3 53 110 1700 64 78 4500 58 6.2 11 65 µg/kg Dry Weight (Parts per Billion (ppb) Dry) 1200 63 670 29 690 73 650

Source: Washington State Department of Ecology Toxic Cleanup Program. 2008. Sediment Quality Chemical Criteria. http://www.ecy.wa.gov/programs/tcp/smu/sed_chem.htm. Note: a. Where laboratory analysis indicates a chemical is not detected in a sediment sample, the detection limit shall be reported and shall be at or below the Marine Sediment Quality Standards chemical criteria value set in this table. b. Where chemical criteria in this table represent the sum of individual compounds or isomers, the following methods shall be applied: i. Where chemical analyses identify an undetected value for every individual compound/ isomer then the single highest detection limit shall represent the sum of the respective compounds/isomers; and ii. Where chemical analyses detect one or more individual compound/isomers, only the detected concentrations will be added to represent the group sum. c. The listed chemical parameter criteria represent concentrations in parts per million, “normalized,” or expressed, on a total organic carbon basis. To normalize to total organic carbon, the dry weight concentration for each parameter is divided by the decimal fraction representing the percent total organic carbon content of the sediment. d. The LPAH criterion represents the sum of the following “low molecular weight polynuclear aromatic hydrocarbon” compounds: Naphthalene, Acenaphthylene, Acenaphthene, Fluorene, Phenanthrene, and Anthracene. The LPAH criterion is not the sum of the criteria values for the individual LPAH compounds as listed. e. The HPAH criterion represents the sum of the following “high molecular weight polynuclear aromatic hydrocarbon” compounds: Fluoranthene, Pyrene, Benz(a)anthracene, Chrysene, Total Benzofluoranthenes, Benzo(a)pyrene, Indeno(1,2,3,-c,d)pyrene, Dibenzo(a,h)anthracene, and Benzo(g,h,i)perylene. The HPAH criterion is not the sum of the criteria values for the individual HPAH compounds as listed. f. The TOTAL BENZOFLUORANTHENES criterion represents the sum of the concentrations of the “B,” “J,” and “K” isomers.

284


Wisconsin State of Wisconsin, Department of Natural Resources, Consensus Sediment Quality Guidelines, Recommendations for Use and Application, Interim Guidance, Contaminated Sediment Standing Team. WT-732 2003. Dec. 2003. http://dnr.wi.gov/org/aw/rr/technical/cbsqg_ interim_final.pdf.

Europe European Legislation EC Legislation Several western European countries have developed their own placement policies or guidelines, but certain EC Directives govern the Placement and/or use of dredged material in EC countries under the definition of “waste.” This section reviews both the EC Directives and the individual countries’ policies. Classification of Dredged Material in the EC Region Several EU Member States have defined or proposed sediment quality levels that trigger various levels of action. While definitions vary, they may be generalized as: Class 1—Below action Level 1: sea Placement permitted Class 2—Between Action Levels 1 and 2: sea placement permitted with restrictions (e.g., monitoring) Class 3—Higher than Action Level 2: sea placement permitted only under very specific conditions Here are some of the individual states.

Belgium Sediment Quality Criteria for Belgium, on Metals and Organics in Dredged Material Parameter

Action Level 1 (Target Value) (ppm D.M.)

Action Level 2 (Limit Value) (ppm D.M.)

0.3 2.5 70 160 70 20 60 20 3 14 mg/goc 70 µg/goc 2 µg/goc

1.5 7 350 500 280 100 220 100 7 36 mg/goc 180 µg/goc 2 µg/goc

Hg Cd Pbd Zn Ni As Cr Cu TBT Mineral oil PAHs PCBs GOC, gram organic carbon

285


Finland The action levels for dredged material in Finland were adopted by the ministry of the Environment on 19 May 2004. These values are still, however, guidance values and not binding forms. The aim is to be able to give binding norms within a few years. All measured contaminant contents are normalized to a “standard soil” composition (10% organic material and 25% clay). The values in the table refer to the normalized values.

Contaminant Hg Cd Cr Cu Pb Ni Zn As PAHs Naphthalene Anthracene Phenanthrene Fluoranthene Benzo[a]anthracene Chrysene Benzo(k)fluoranthene Benzo[a]pyrene Benzo[ghi]perylene Indeno(123-cd)pyrene Mineral oil DDT+DDE+DDD

Action Level 1 (ppm Dry Weight) 0.1 0.5 65 50 40 45 170 15

1 2.5 70 290 200 60 500 60

0.01 0.01 0.05 0.3 0.03 1.1 0.2 0.3 0.8 0.6 500 0.01

0.1 0.1 0.5 3 0.4 11 2 3 8 6 1500 0.03

ppb Dry Weight PCB (IUPAC-numbers) 28 52 101 118 138 153 180 Tributyltin (TBT)

Dioxins and furans (PCDD and PCDF)

Action Level 2 (ppm Dry Weight)

1 1 4 4 4 4 4 3 ng WHO-TEQ/kg 20

ppb Dry Weight 30 30 30 30 30 30 30 200 ng WHO-TEQ/kg 50

286


France If analysis shows that concentrations are less than action level 1, a general permit is given without specific study. If analysis shows that concentrations exceed action level 2, dumping at sea may be prohibited, especially when this dumping does not constitute the least detrimental solution for the environment (particularly with respect to the other solutions, in situ, or on land). These values do not consider the toxic character and bioavailability of each element. If analysis shows that concentrations are situated between action level 1 and action level 2, a more comprehensive study might be necessary. The content of these studies will be established on a case-by-case basis, taking account of the local circumstances and the sensitivity of the environment. The action levels are shown in the following table.

Substances



Substance

0.4 1.2 25 100 90 45 276 37

0.8 2.4 50 200 180 90 552 74

CB 28 52 101 118 180 138 153 Total PCBs

Metals Hg Cd As Pb Cr Cu Zn Ni



PCB 0.025 0.025 0.050 0.025 0.025 0.05 0.05 0.5

0.05 0.05 0.05 0.10 0.05 0.10 0.10 1.0

Germany Sediment Quality for the German Federal Waters and Navigation Administration on Trace Metals and Organic Contaminants in Dredged Material (Sediment Fraction15000 >1.5

Organic Component (ppb Dry Weight) Sum PAH (EPA 16)

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